Despite his optimism, the Trump administration has not committed to providing federal financing for the tunnel, raising questions about whether it supports the project. The federal Transportation Department recently withdrew from the Gateway corporation board, saying that it did not want to appear to favor the tunnel over projects elsewhere in the country.

Elaine Chao, the transportation secretary, has said that she and President Trump understand the tunnel’s importance, but the administration has proposed cutting a grant program that could have helped pay for the project. The Obama administration strongly supported building a new tunnel and had agreed to join with Amtrak to cover half of the project’s cost. Gov. Andrew M. Cuomo of New York and Gov. Chris Christie of New Jersey have agreed to finance the other half.

The construction of a new tunnel could begin by fall 2019, and the tunnel could open in spring 2026, according to the report, which estimated the cost of the new tunnel at $11.1 billion. Rehabilitating the existing tunnel could cost $1.8 billion, the report said.

The century-old tunnel that Amtrak and New Jersey Transit trains now use to cross the Hudson was heavily damaged by Hurricane Sandy in 2012 and has become increasingly unreliable. Local officials worry that the tunnel will continue to deteriorate, requiring major repairs that would wreak havoc on commuting in the region.