In a hearing on Friday, senators pressed Dr. Mehmet Oz, the TV celebrity nominated to head Medicare and Medicaid, on Republican-led proposals that would significantly affect the health care coverage for nearly half of all Americans.

At his confirmation hearing before the Senate Finance Committee, Dr. Oz bantered with senators in a friendly atmosphere, joking about basketball and allegiances to college teams. He largely escaped tough questions from either side of the aisle, displaying his on-air charm as he deflected Democrats’ most pointed concerns about potentially radical changes in health coverage for not only those 65 and older but also for poor children.

Many senators seemed distracted by the fierce debate over the Republicans’ budget deal to avert a government shutdown, and they dashed in and out of Dr. Oz’s hearing. But he is poised to sail through the Senate for confirmation as the next administrator of the Centers for Medicare and Medicaid Services, an agency with $1.5 trillion in spending.

Senator Elizabeth Warren, Democrat of Massachusetts, made a big deal of his financial conflicts before the hearing. But at the session, she did not press him on those issues. Instead, she focused on his views about whether private Medicare plans are overcharging the government, an area where she and Dr. Oz seemed to agree on the need to tackle potential fraud and waste.

Throughout the hearing, he displayed a facile knowledge of a variety of relevant agency issues, although he repeatedly reverted to stock answers that he would need to study the topic at hand more.

Several lawmakers, mainly Democrats, tried to force Dr. Oz to express his views on the Trump administration’s goals to cut back on health care costs and agency budgets, but he repeatedly sidestepped those minefields.

“It is our patriotic duty to be healthy,” he told senators. “It costs a lot of money to take care of sick people who are sick because of lifestyle choices.”

This refrain is in line with the Make America Healthy Again movement championed by Robert F. Kennedy Jr., the new secretary of the Department of Health and Human Services, and Dr. Oz’s soon-to-be boss if he is confirmed.

Medicare Advantage and privatization

Introductory remarks from Senator Ron Wyden, Democrat of Oregon, held out an initial promise of some challenging questions. He accused Dr. Oz of dodging almost $500,000 in Social Security and Medicare taxes in recent years by using a tax exemption related to limited partnerships, something Democrats concluded after reviewing Dr. Oz’s tax returns. But there were no follow up questions on it.

Mr. Wyden also raised the specter that he was going to grill Dr. Oz on his connection to TZ Insurance Solutions, a for-profit company that sells Medicare Advantage plans to older Americans. Dr. Oz has been a relentless promoter of these private plans, which have been criticized by lawmakers and regulators for systemic overbilling and denying patients care, on his show and YouTube channel.

Dr. Oz, 64, is also a registered broker for TZ Insurance in states across the country, according to a recent investigation into his finances by The New York Times. Again, Mr. Wyden flagged the issue and did not follow up.

Despite concerns by Democrats that Dr. Oz would most likely roll back some of the rules meant to rein in the plans, he instead committed to strong oversight. He acknowledged that some of the brokers now selling these plans were “churning policies,” switching people from one plan to another, regardless of whether the change in coverage benefited them.

“Part of this is just recognizing there’s a new sheriff in town,” Dr. Oz said. “We actually have to go after places and areas where we’re not managing the American people’s money well.”

Several times in the hearing, Dr. Oz addressed bipartisan concerns over whether Medicare Advantage plans are overpaid. In response to questions from a fellow physician, Senator Bill Cassidy, Republican of Louisiana, Dr. Oz mentioned a study suggesting the federal government spends more on the private alternative to Medicare than the government-run program. “It’s upside down,” he said.

“We should examine whether some of the money should be reimbursed to the American people,” Dr. Oz said.

He also expressed interest in solving some of the bipartisan concern over insurers’ use of prior authorization for approving medical procedures by reducing the number of services that would be subject to review.

Republican plans to cut Medicaid

Democrats seemed most frustrated by Dr. Oz’s stance toward Medicaid, the state-federal program that covers 72 million low-income Americans. “All my colleagues want to know, are you going to cut Medicaid?” asked Senator Maria Cantwell, Democrat of Washington.

But Dr. Oz, who has not spoken much about the program he would also oversee as head of the agency, did not answer directly. He said he did not know the details of the Republican budget discussions, in which lawmakers are looking at hundreds of billions of dollars in cuts that could result in people’s loss of coverage as it became more difficult to enroll and states had to shoulder more of the burden.

When questioned by Senator Raphael Warnock, Democrat of Georgia, about Republican efforts to add burdensome monthly paperwork for some people to show they should get benefits, Dr. Oz said he favored the work requirements that Republicans want to limit eligibility. But he agreed with the senator about making sure people who should be eligible for Medicaid were not cut off.

Dr. Oz and his supplement business

There were other subjects senators seemed to veer away from. For instance, Dr. Oz has made tens of millions of dollars over the years promoting dietary supplements, often without any mention of his financial interest. He has been paid by numerous medical and health firms for showcasing their products. Many of those companies would be affected by any decisions he would make as the administrator for the Centers for Medicare and Medicaid Services, and many already benefit from agency funding.

Senator Maggie Hassan, Democrat of New Hampshire, asked him to put a dollar figure on exactly what he has made from promoting supplements on his daytime TV show. He said he was not paid anything. He started to explain that Sony Pictures distributed the show, and that it was the entity paid by these companies (which in turn paid him), but he was cut off. Ultimately, Ms. Hassan was unable to extract anything meaningful from him and moved on.

Patient privacy and the DOGE intrusion

In the hearing, Mr. Wyden pressed Dr. Oz about the access granted to Elon Musk’s so-called Department of Government Efficiency to Americans’ private medical information. Mr. Wyden raised concerns about the need to protect people’s privacy given the department’s potential ability to view personal health and medical data. Despite his repeated questions, he said, the Trump administration had so far not addressed those concerns. Surprisingly, Dr. Oz said he had no discussions with the administration about what Mr. Musk’s team was doing as it inspected agency information, but he promised to “address what is going on.”

Measles

The measles outbreak in Texas and New Mexico has heightened concerns and leveled significant criticism at the response by Mr. Kennedy and the Trump administration. Senator Ben Ray Luján, Democrat of New Mexico, asked Dr. Oz whether he believed the measles vaccine was safe. Dr. Oz said he did, but when the senator followed up by asking whether it was effective, Dr. Oz stepped back and said that judging individual vaccines and their recommendations for use would not be under his purview but under that of the Centers for Disease Control and Prevention.

“My job, if confirmed, is to make sure we pay for those vaccines,” he said.

China and Russia joined Iran on Friday in urging an end to Western sanctions after President Trump called this week for nuclear talks with Tehran, with both countries denouncing the “threat of force.”

After talks in Beijing with the deputy foreign ministers of Russia and Iran to discuss Iran’s nuclear program, the Chinese government said the three countries had agreed that all parties should “abandon sanctions, pressure and threats of force.”

That appeared to be a reference to recent overtures that Mr. Trump has made toward Iran. Mr. Trump said last week that he had sent a letter to the Iranian government seeking to negotiate a deal to prevent Tehran from acquiring a nuclear weapon. But he warned that the country would have to choose between curbing its fast-expanding program and losing it in a military attack.

The meeting was the latest sign of Beijing’s close alignment with Moscow and Tehran, and of its ambition to become a key arbiter of international disputes. Earlier this week, the three countries held joint naval drills in the Gulf of Oman.

China and Russia are taking a very different approach to Iran now than they did a decade ago. In 2015, they insisted on first reaching a deal with Iran to stop its nuclear weapons program before ending sanctions. Russia even took a lot of Iran’s nuclear fuel stockpile as part of that arrangement.

The United States is now pursuing maximum political pressure with a threat of military action. But China and Russia are pursuing a more cooperative and conciliatory approach. This means that major powers are divided on how to approach Iran, which may give Tehran more diplomatic room to maneuver.

“Russia and China are also signaling to other countries that there are alternatives to U.S. global leadership — that Moscow and Beijing are responsible global actors that can address major global challenges like nuclear weapons,” said Andrea Kendall-Taylor, a senior fellow at the Center for a New American Security, a Washington research group.

The most concerning part of the Iranian program is the production of potential nuclear weapons material that has been enriched to 60 percent purity, which is nearly bomb-grade. It could take a week or so to convert it to the 90 percent purity required for use in bombs that produce large nuclear detonations. Experts believe Iran may now have enough for roughly six weapons.

Russia and China did not present a plan to remove or reduce in purity the Iranian supply of potential nuclear weapons material. Nor did they address Iran’s installation of more advanced centrifuges, which will increase the size of the country’s stockpile of enriched material.

The Iranian government said in late November that it would begin operating the advanced centrifuges to enrich more uranium, which could bring it closer to having a nuclear weapon.

Wang Yi, China’s foreign minister, issued a five-point plan for addressing Iran’s nuclear program. While calling for an end to sanctions on Iran, the plan also urged Iran to “continue to abide by its commitment not to develop nuclear weapons.”

Beijing wants to show that “while the United States irresponsibly pulls out of the Iran Nuclear Agreement, China will also hold fast to this international commitment and assume the responsibility of leadership,” said Shen Dingli, an international relations scholar in Shanghai.

The message is also one of solidarity with Iran. “Even though the United States exerts extreme pressure, as long as Iran does not give up on its relevant commitments, it will still have friends,” Mr. Shen said. “Iran doesn’t need to worry. In the end, this is a strategic game between China and the United States.”

Iran’s supreme leader last week decried “bullying governments” and seemed to push back on the idea of negotiating with the United States.

China and Russia’s support could help Iran seem less isolated, but Tehran might have concerns, as well.

“The Iranians, for their part, are very wary of Chinese, but especially of Russian involvement in negotiations, as they fear they will be sold out by Moscow as part of a broader U.S.-Russia accord,” said Gregory Brew, a senior analyst at the Eurasia Group. “They will be looking for support from Russia while resisting any pressure to give in to U.S. demands.”

China has considerable leverage over Iran: Chinese companies purchased over 90 percent of Iran’s oil exports last year, often at deep discounts to world prices, according to Kpler, a Vienna-based company that specializes in tracking Iran’s oil shipments. Most other countries have refrained from buying oil from Iran so as to comply with Western-led sanctions aimed at persuading Iran to stop its development of nuclear weapons.

Sales by Iran’s state oil company to China represent about 6 percent of Iran’s entire economy, or half of government spending in Iran.

David E. Sanger contributed reporting from Washington and David Pierson from Beijing.