Sen. Chuck Schumer, the incoming Senate minority leader, said Monday he favored a 10-year, trillion-dollar infrastructure bill — an idea put forth by Republican President-elect Donald Trump during his campaign.

But how to pay for it remained an issue. The bill “must be fueled by substantial and direct federal funding,” the senator said at a news conference at the Long Island Rail Road station in Ronkonkoma, where he touted the potential benefits such spending would have for the Island.

Advisers to Trump have floated the idea of having private investors build roads, bridges and work on sewer projects in return for tax incentives or user fees levied on the finished project.

Schumer (D-New York) said he would oppose any infrastructure proposal “that is made up of gimmicks or tax breaks that don’t actually help move the economy forward.”

“The first 100 days of this new administration could provide us with a real shot at fixing aging sewers, roads and bridges,” Schumer said.

Schumer was joined at the news conference by Marc Herbst, executive director of the Long Island Contractors Assocation; Mark Epstein, chairman of the Long Island Rail Road Commuter Council and other advocates.

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“Long Island Rail Road riders struggle daily commuting on a railroad with inadequate capacity, outdated and aging control and signal systems, and stations that do not meet riders’ needs,” Epstein said. “Increased funding is critical to relieving these problems for long suffering LIRR commuters and [I] hope the new Congress will support Senator Schumer’s lead.”

Schumer said some of the big projects that could help Long Island included a second LIRR track, being built between Ronkonkoma and Farmingdale, and the East Side Access project to extend the LIRR in Manhattan to Grand Central Terminal.

Schumer said the second track must be a “top priority” because it would radically reduce commuting times, facilitate the flow of workers into and out of Long Island, and spur the growth of jobs and MacArthur Airport.

The senator said one of every four wastewater treatment plants in New York State is operating beyond its useful life, and that almost one-third of the state’s 22,000 miles of sewers are more than 60 years old.

All these projects, he said, would make Long Island and New York more competitive for new and existing businesses.

“Though the devil is in the details, it is clear that Long Island is ready, willing and able to make these repairs. We just need the funding to get the job done,” Schumer said.