Republicans are preparing to cut taxes, slash spending and slow immigration in a broad agenda that will require unifying an unruly party behind dozens of complicated policy choices.

For now, though, they are struggling with a more prosaic decision: whether to cram their policy goals into one bill or split them into two.

It is a seemingly technical question that reveals a fundamental divide among Republicans about whether to prioritize a wide-ranging crackdown on immigration or cutting taxes, previewing what could be months of intramural policy debate.

Some Republicans have argued that they should pass two bills in order to quickly push through legislation focused on immigration at the southern border, a key campaign promise for Mr. Trump and his party’s candidates. But Republicans devoted to lowering taxes have pressed for one mammoth bill to ensure that tax cuts are not left on the cutting-room floor.

President-elect Donald J. Trump met with Republican senators in Washington on Wednesday, as those lawmakers sought clarity on his preferred strategy. He has waffled between the two ideas, prolonging the dispute.

“Whether it’s one bill or two bills, it’s going to get done,” Mr. Trump told reporters after the meeting.

Republicans are planning to ram the partisan fiscal package through the Senate over the opposition of Democrats using a process called reconciliation, which allows them to steer clear of a filibuster and pass bills with a simple majority vote. But for much of this year, Republicans will be working with a one-seat majority in the House and a three-seat majority in the Senate, meaning they will need near unanimity to pass major legislation.

That has left some worried that it will be hard enough passing one bill, much less two.

“There’s serious risk in having multiple bills that have to pass to get your agenda through,” Representative Steve Scalise of Louisiana, the majority leader, said. “When you know you’ve got a lot of people that want this first package, if you only put certain things in the first package, they can vote no on the second and you lose the whole second package. That would be devastating.”

Adding to the urgency of achieving their policy goals, Republicans are facing a political disaster should they fail to deliver. Many of the tax cuts they put into place in 2017, the last time Mr. Trump was president, expire at the end of the year. That means that taxes on most Americans could go up if Congress does not pass a tax bill this year.

Passing tax cuts can take time, though. While much of the Republican tax agenda involves continuing measures the party passed in 2017, Mr. Trump and other Republicans have floated additional ideas, including no taxes on tips and new incentives for corporations to manufacture in the United States. Ideas like that could take months to formulate into workable policy.

Then there is the gigantic cost. The nonpartisan Congressional Budget Office estimates that simply extending the 2017 tax cuts would cost more than $4 trillion over a decade — a price tag that would grow if other tax cuts, like Mr. Trump’s proposal to not tax overtime pay, are included.

Further complicating support for the legislation is that Republicans plan to raise the debt limit through reconciliation, another sensitive issue for fiscal hawks.

Members of the ultraconservative House Freedom Caucus have said they would not support any legislation unless the costs it introduces are offset by spending cuts. While most Republicans support reining in federal spending, agreeing on which federal programs to slash always proves harder than expected. In an attempted workaround, Republicans have instead begun to explore ways to change Washington’s budget rules so the tax cuts are shown to cost less.

The complexity of pulling together a tax bill that can secure the necessary votes has some Republicans hoping to hold off until later in the year and first charge ahead with a smaller bill focused on immigration, energy and military issues. Republicans have not yet publicly sketched out what that bill would look like.

Proponents of that strategy argue it would deliver Mr. Trump an early political victory on immigration and treat a top Republican campaign issue with the urgency it deserves.

“The No. 1 priority is securing our border,” Representative Byron Donalds of Florida told reporters on Tuesday. “In my opinion it’s the top priority, and everything else is a close second.”

Senator Lindsey Graham of South Carolina, the chairman of the Budget Committee who will be overseeing the reconciliation process, has also pressed for a two-bill approach. “If you hold border security hostage to get tax cuts, you’re playing Russian roulette with our national security,” he said.

Republicans have looked to Mr. Trump to intervene and set a clear direction for the party. On Sunday, he wrote on social media that Congress should pass “one powerful Bill,” an apparent victory for lawmakers like Representative Jason Smith of Missouri, the chairman of the House Ways and Means Committee, who had championed that approach. Mr. Trump’s equivocation since then, though, has left Republicans still unsure of which strategy they should pursue.

Mr. Trump’s meeting with top Republican senators on Wednesday will be followed by a discussion with various House Republicans in Florida over the weekend.

In a sign of how politically complicated the tax cut discussion could get, one of the sessions is expected to focus on relaxing the $10,000 limit on the state and local tax deduction, known as SALT.

Republicans included the $10,000 limit in the 2017 tax law as a way to contain the cost of that legislation. But the move angered House Republicans from high-tax states like New York and New Jersey, many of whom voted against the entire 2017 tax bill as a result. Such defections are a luxury that Republican leaders can’t afford this year given their narrow majority.

G.O.P. lawmakers from New York, New Jersey and California could tank a tax bill if they are unsatisfied with how the provision is handled. They are now pushing to lift the cap as part of the party’s tax bill. Eliminating the cap entirely could add roughly $1 trillion to the price tag of the legislation.

Maneuvering ambitious policy agendas through Congress has often been a messy and time-consuming process for presidents. A Republican effort to repeal the Affordable Care Act during Mr. Trump’s first term collapsed after more than six months of discussion.

After quickly passing pandemic relief measures in 2021 under President Biden, much of Democrats’ broader agenda was stymied for almost two years before a second party-line measure passed that was far narrower than many in the party had hoped.

This time around, Republicans will be grappling not only with a historically slim margin in the House, but also a president prone to sudden changes of heart.

“You can argue the merits of both” strategies, said Representative Jodey Arrington, a Texas Republican who leads the House Budget Committee. “He has to tell us what he wants and what he needs.”

In the days after Donald J. Trump was re-elected president, one of his most high-profile stops was at an Ultimate Fighting Championship event at Madison Square Garden.

Mr. Trump’s appearance in the front row was notable, as was the presence of some of his closest confidants, like Elon Musk, who sat alongside him. But few in attendance for the fights would have recognized the other man sitting beside the president-elect.

Yasir al-Rumayyan, the governor of Saudi Arabia’s vast sovereign wealth vehicle, the Public Investment Fund, watched the action from ringside, and is getting even closer to being part of the action. A company owned by the fund is close to creating a boxing league with TKO, the owner of Ultimate Fighting Championship. A deal for what would be a new competition, featuring up-and-coming boxers tied exclusively to the league, could be announced within weeks, according to three people familiar with the matter.

TKO said in a statement on Wednesday that it had “nothing to announce,” but that it “would evaluate any unique and compelling opportunity that could fit well in our portfolio of businesses and create incremental value for our shareholders.”

The wealth fund did not comment.

The potential investment in TKO follows a Saudi Arabian effort in June to create a multibillion-dollar boxing league that would aim to unite the world’s best boxers, who for decades have been divided by rival promoters and fighting for titles controlled by an alphabet soup of sanctioning bodies. That effort, while not completely abandoned, had proved complicated and expensive, even for a country like Saudi Arabia, which for the past half decade has disbursed billions to become a player across some of the world’s biggest sports.

The investment in the new league will be made by Sela, a subsidiary of the Public Investment Fund. TKO — which is majority controlled by the entertainment and sports conglomerate Endeavor and embodied by Dana White, the U.F.C. empresario, a longtime friend of Mr. Trump’s — would be a managing partner. In return, TKO has been offered an equity stake and a share of the revenue, according to the people familiar with the matter, who spoke on the condition of anonymity ahead of the official announcement.

Saudi Arabia has backed some of the biggest and richest boxing bouts in history in recent years. It has played host to major title fights, most recently a face-off between Oleksandr Usyk and Tyson Fury, which ended with Mr. Usyk as the first undisputed heavyweight champion in more than a generation. Fights like that, which for years proved almost impossible to negotiate, have taken place thanks to the millions of dollars put on the table by Turki al-Sheikh, a government official with close ties to the kingdom’s crown prince, Mohammed bin Salman.

Mr. al-Sheikh, a former security guard, has become perhaps the most powerful man in boxing, seen at ringside and even inside the ring for the biggest bouts. He is also a frequent recipient of messages of thanks from some of the best-known fighters and boxing promoters, who refer to him as “His Excellency.” He pushed for a partnership with Mr. White, who over the last two decades has turned the U.F.C. from a $2 million company into one worth more than $10 billion. Talks have been taking place for more than a year in the United States, Europe and Saudi Arabia.

Mr. al-Sheikh had suggested in interviews that he was planning a new boxing venture. And he has made no secret of his frustration at the way the sport has been run, with the best fighters rarely meeting in their prime. In November, he purchased Ring Magazine — the century-old bible of the sport — and vowed to re-establish its prominence.

Mr. al-Sheikh has also teamed up with the World Boxing Council, a sanctioning organization, to create the Boxing Grand Prix, a tournament for young boxers.

For TKO, which owns both the U.F.C. and World Wrestling Entertainment, the venture has little risk, given that the Saudis are footing the bill. “If we were to get involved in boxing, we would expect to do so in an organic way, not an M&A way,” said Mark Shapiro, TKO’s president, on an earnings call in November, referring to mergers and acquisitions.

He added, “So, i.e., we’re not writing a check.”

Should the deal be completed, TKO will earn management fees of close to $30 million a year. Saudi Arabia is expected to pay significantly more in hosting fees to the league than any other country, according to details of the plan reviewed by The New York Times. Two fights there will bring in more than $40 million in fees. Other bouts are planned for the United States and Europe, where the hosting fees will be far lower.

TKO has also been talking with other parties, including other Arab nations, about the boxing league, according to one of the people familiar with the matter.

Endeavor, TKO’s parent company, has at times had a strained relationship with Saudi Arabia, and this potential partnership suggests that it has largely been repaired. In 2019, after the killing of the Saudi journalist Jamal Khashoggi, Endeavor returned $400 million that the Saudi sovereign wealth fund had invested in the company.

For the Saudis, getting a partner like Mr. White would come at an opportune time. He joined the board of Meta this week, and has spoken at the last three Republican National Conventions. Mr. Trump regularly hosted U.F.C. events at his properties in the organization’s early years, and he has attended many fights. Mr. Trump and Mr. al-Rumayyan are also close, with the Saudi-owned LIV golf championship holding several of its events at Mr. Trump’s courses, including one scheduled for April in Florida.

Saudi officials have described sports and entertainment as major pillars of a strategy, known as Vision 2030, to pivot their economy away from its reliance on oil exports, and as a part of efforts to liberalize society. Critics have described those efforts differently, positioning them as a way of using sports to distract the focus from Saudi Arabia’s human rights record, a tool known as sportswashing.

What TKO would get is a partnership with the biggest sports investor in the world. Saudi Arabia has invested in teams, talent and events across a wide range of sports, most recently securing rights to the 2034 men’s soccer World Cup, the most-watched event on the planet.

The U.F.C.’s U.S. media rights agreement with ESPN expires this year, as does the network’s deal with Top Rank, a top boxing promoter. TKO could try to bundle the rights to its new boxing league with the U.F.C. rights to help shore up the fledgling boxing league.

But applying the U.F.C. playbook to boxing will be extremely difficult. Boxing is a much more heavily regulated sport than mixed martial arts, with the federal Muhammad Ali Act mandating a separation in boxing between the role of manager and promoter, and the public listing of purse figures.

Unlike U.F.C., the league would not include the most prominent boxers. And they may not think there is an upside to joining it. While the fractured nature of boxing means its earning potential isn’t maximized for promoters and managers, top boxers earn far more than top M.M.A. fighters.

In October, the U.F.C. settled an antitrust lawsuit filed by former fighters — who claimed that the company illegally suppressed fighters’ pay — for $375 million. Documents submitted as evidence in that suit showed that the U.F.C. paid less than 20 percent of its revenue to its fighters.

In boxing, those figures are reversed, with fighters combining to earn well over 50 percent of the revenue from any fight.