The Hudson River tunnel, used by 450 Amtrak and New Jersey Transit trains each weekday, may shut down in seven years without proper funding to rebuild it, Sen. Charles Schumer warned Monday.

"There might be no tunnel under the Hudson," he said. "Imagine, ferrying hundreds of thousands of workers across the river."

He said that a new federal transportation bill, which passed Congress last week and is expected to be signed soon by President Barack Obama, could be a big boon to the massive rebuilding plan and help finance it.

The project, called the Gateway Program, will cost about $20 billion. In addition to the tunnels, it includes a connection between Penn Station and the future Moynihan Station, which is being built at the Farley Post Office building.

"Just because it's seven years away, doesn't mean we should be sitting here, twiddling our thumbs, and doing nothing for the next five years," Schumer said.

The bill changes the structure of Amtrak so that it can reinvest profits from its popular Northeast Corridor route into big capital projects in the region. Currently, that money is used to subsidize lines in other parts of the country, officials said.

That money then creates a revenue stream that can be used to borrow additional money, Schumer added.

The bill also changes two federal programs to make it easier to get low-interest loans and grants for passenger rail projects.

The tunnel under the Hudson River is 105 years old and had significantly deteriorated before it was devastated by salt water from Superstorm Sandy.

In November, an agreement was reached to form a corporation within the Port Authority to handle its replacement.

The federal government said it would pick up half the tab, but it was not immediately clear how it would be financed.

The transportation bill opens up new ways to finance the new tunnel, which is the biggest infrastructure project nationally in decades, officials said.