Officials from New Jersey and New York convened in Manhattan on Monday to celebrate a funding agreement that finalizes a long-awaited cross-Hudson rail project that will double capacity and boost the reliability of the plagued railway.

Monday morning’s signing ceremony served as a victory lap for the Gateway project’s advocates, who credited the Biden administration for the $6.8 billion grant that pushed the railway expansion to the “point of no return.” The federal government will now cover about 70 percent of the cost of the Gateway Program, which consists of a series of bridge and tunnel projects planned through 2038.

The project is expected to stabilize the stretch of troubled tracks — NJ Transit commuters have faced repeated hours-long delays in recent weeks after Amtrak-managed railways suffered wiring issues.

The Biden administration’s $12 billion total commitment to the Gateway project constitutes the largest federal investment in a rail transit project in modern history. Loans from the Build America Bureau reaching $4.06 billion will cover the local share of the cost.

“Today is a day of making investments, the biggest investment of taxpayers in a transportation project ever,” said Senator Cory Booker. “This is a day of coming back to who we say we are, a nation that invests in itself so we can grow our nation, grow our economy, and continue to lead the world.”

Democrats used the event to laud President Joe Biden, who has faced some pressure to end his reelection campaign after a middling debate performance last month.

Booker, for example, said former President Donald Trump held up environmental reviews and other steps necessary for the project.

“If there’s any reason we’re here today, it’s because when President Joe Biden was elected, he said this is the No. 1 infrastructure project in the United States of American,” Booker said. “And I want to thank President Joe Biden for his focus, for his commitment, and for helping us in Congress, in the Senate, to deliver what we see today.”

And Deputy Transportation Secretary Polly Trottenberg, who represented the administration at the ceremony, criticized Trump for “racking up costs and delaying this important work.”

“He really is Amtrak Joe,” Trottenberg said. “I’m proud to say we are all in, from the top to bottom.”

Expect New Jersey Republicans to also tout Gateway as a victory: Rep. Tom Kean (R-Westfield), who faces a tight reelection race against Sue Altman, has used his seat on the House Transportation & Infrastructure Committee to push for the Gateway project.

Construction on one part of the project, the new Portal North Bridge spanning the Hackensack River, started two years ago, but the funding agreement wraps up a yearslong fight to secure money for what will be a decade-long project.

The Gateway project includes the construction of two new rail tunnels and the revamp of the existing North River Tunnel — the new tunnels are projected to enter service in 2035, and the revamp is expected to conclude in 2038. The Portal North Bridge, which replaces the more than century-old Portal Bridge that is a regular source of delays and congestion, is scheduled for a 2025 partial completion.

Later stages of the project, which include a planned expansion of New York Penn Station, will make possible a four-track railway from Newark Penn Station to New York.

“Please have some patience, this is not going to be overnight,” Gov. Phil Murphy said during the event. “But when it finally hits, it will transform literally millions of lives, and I’m honored to be a part of that.”

Tony Coscia, the chair of Amtrak’s Board of Directors and the vice chair of the Gateway Development Commission, said the project will double NJ Transit and Amtrak capacity from 450 trains per day to 900.

“The new Hudson River Tunnel will supercharge the rail connections across our region and to the nation, improving and expanding rail service in ways we’ve only been able to dream about in the past,” Coscia said in a release.

Senator Bob Menendez, a staunch proponent of the Gateway program, was absent from the ceremony — his corruption trial is approaching closing arguments — but offered his praise in a statement Monday.

“Hard-working New Jerseyans have waited too long for faster, safer, and more reliable public transit along the Northeast Corridor, and now help is on the way,” Menendez said.

Memories of former Gov. Chris Christie’s cancellation of a prior rail project hung heavy over the proceedings — several speakers lauded the expansion but said it should have started years ago. Christie in 2010 controversially pulled New Jersey out of the ​​Access to the Region’s Core project, which started in 2009 and was slated for completion in 2018.

“Like a lot of you, I too in the Obama administration had the heartbreaking experience of watching a previous New Jersey governor cancel the original project,” Trottenberg said. “It was such a frustrating moment.”

But at Monday’s celebration, officials thanked themselves, their counterparts from across the Hudson, and the Biden administration for building the framework of the landmark project.

“The Gateway race was truly a marathon, with its twists, its turns, its bumps,” Senate Majority Leader Chuck Schumer said at Monday’s signing ceremony. “But we laced up, we kept up the pace, and we made it.”