Amtrak chairman Tony Coscia on Tuesday described last week’s joint meeting with the Trump administration on the Gateway Program as “very productive,” but warned that costs to build new rail tunnels under the Hudson River would balloon if funding isn’t secured soon.

“From all accounts it was, I think, a very productive meeting,” Coscia told reporters after giving a speech on transit at an Association for a Better New York breakfast. “I think it gave opportunity for all the key stakeholders to sort of share their views and for the administration to ask questions that I think are good questions about the project and its significance and options for funding it.

“From our perspective, having our stakeholders at that level talking to each other is a very, very positive development,” he added.

The $24 billion Gateway Program would dig a new rail tunnel under the Hudson River, expand Penn Station and build new bridges to better connect Newark, New Jersey, and New York City. While replacing debilitated infrastructure, the program would also improve capacity for the growing number of people making the cross-Hudson commute.

Transit advocates and elected officials have billed the construction of a new Hudson River tunnel, the key component of the program, as the most important infrastructure project in the nation. The current tunnels were badly damaged by superstorm Sandy. Amtrak has described a ticking time bomb scenario where if one of the tunnel’s two tubes fails before a new tunnel is constructed, rail capacity under the Hudson would be reduced by 75 percent.

Coscia said preliminary Gateway construction will continue through March 2018, when Gateway’s environmental review process will be completed. At that point, Amtrak hopes to have funding secured to keep the project moving smoothly into its next construction phase.

“We’re going to continue the path that we’ve already started of marching toward building this project and then in 2018, hopefully without any significant interruption, we’re going to move to the next phase,” he said, “because by then we will have accomplished an ability to develop a plan of finance for the project that will allow us to initiate construction on the tunnel program.

“Whether that happens or not, I guess we’re all going to see,” Coscia said.

Representatives from New Jersey and New York, including Gov. Andrew Cuomo and Sen. Chuck Schumer, also joined in the meeting last week. Coscia’s comments were largely in line with those of the governor and the Senate minority leader. Amid fears of funding concerns, the elected officials are seeking the Trump administration to honor the Obama-era commitment to fund half the total costs of Gateway.

“Getting this done is essential. And it is expensive. But the cost we’d pay for failure would be far, far greater,” Schumer said of Gateway, during a news conference with reporters on Sunday. “[Trump] seemed open to it. I asked him would he commit after the meeting. He said, ‘Give me a few days and I’ll get back to you.’”

The United States Department of Transportation did not immediately respond to a request for comment.

Estimates for the Hudson River tunnel project have increased from $7.7 billion to nearly $13 billion, according to a recently released report by the Federal Railroad Administration and New Jersey Transit. Coscia said if the government continues to drag its feet on funding commitments, the cost will likely only go up.

“Time is money in the construction business,” Coscia said. “I guarantee you that whatever costs anyone comes up with to build this tunnel today, that if you do the exact same analysis three years from now, the price will be higher. It’s just simply a function of the fact that time creates added level of risk and added level of costs to it.”

Correction: An earlier version of this story had an incorrect title for Tony Coscia. He is Amtrak's chairman.