Could a Trump administration kill the Green Line extension?

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A Green Line train pulled into the Lechmere Station in 2014.Aram Boghosian for The Boston Globe

What will a President Trump mean for the long-awaited Green Line extension into Somerville and Medford?

As political watchers in Washington and beyond try to guess what kind of administration President-elect Donald Trump will run, state transportation officials are also watching how the new administration could affect local funds.

Trump campaigned on a platform that called for heavy infrastructure spending, a sign that could potentially bode well for transportation projects. That appeared to be good news for the embattled Green Line extension that the Massachusetts Bay Transportation Authority is moving forward on — and which is banking on $1 billion from the federal government.

But Trump's controversial — and sometimes contradictory — statements on the campaign trail could cause some uncertainty.

Somerville and Cambridge, both involved in the Green Line extension, are so-called "sanctuary cities," which generally do not cooperate with immigration officials to detain undocumented immigrants. A strong critic of undocumented immigrants during his campaign, Trump made headlines promising an end to federal funding to such cities.

Would moving on those promises cut funding to Green Line extension project, which is counting on that massive federal grant?

If local and national transportation funding watchers are worried, they're not letting on. University of Minnesota's David M. Levinson, a transportation analyst and professor, said that defunding sanctuary cities could affect so many communities that it's essentially a non-starter. And several leaders of sanctuary cities have already said they plan to be defiant if Trump does make good on his promise.

US Representative Michael Capuano, a Democrat from Somerville, said he doesn't see a problem quite yet, adding that officials must see "which part of the rhetoric comes to fruition." Capuano pointed to Trump's promises about rebuilding infrastructure, which the President-elect referenced again in a recent "60 Minutes" interview.

"He's a New Yorker," said Capuano. "He knows how good the subway is, and he has seen how bad New York is when the subway shuts down."

Transportation Secretary Stephanie Pollack, who hasn't commented on the sanctuary city speculation, said recently on WGBH-FM's Boston Public Radio program that big projects tend to survive changes in administration.

In an interview after an MBTA fiscal control board meeting, she has also pointed out that Congress already passed a bipartisan transportation funding deal, referring to a $305 billion highway and transit bill signed by President Barack Obama last December.

"It happened after Paul Ryan was the House speaker, and we're assuming that bill will continue to control our federal funding levels," she said, referring to the Republican from Wisconsin known for his support of austere federal spending. "For right now, we're just going ahead and doing our work as if our federal funding is going to continue at levels that Congress has authorized."

Levinson said it would be unlikely for a new president to try to walk back transportation money that Congress had fought over for years.

"In terms of spending priorities, most money has been allocated from the previous transportation bill," Levinson said. "The question is whether there's new money coming up in anything."

Trump has touted a $3 trillion spending plan that relies mostly on giving incentives to convince private firms to invest in building roads, bridges, and other big transportation projects — but Levinson said that it would likely only apply to select projects with very high returns. And that description doesn't generally apply to the money-losing public transit projects that urban centers need to battle decades of underinvestment.

What if Trump actually wants to make extending transit lines or spending big federal dollars on transportation a priority?

He'll face a skeptical Congress. With Republicans capturing the majority in both chambers, any ambitions for substantially increasing federal funding for transit would likely face a lot of pushback unless it relies on substantial private sector help.

Many transportation watchers are taking a "wait and see" attitude. Pollack said she'll keep talking with the national American Public Transportation Association, and the American Association of State Highway and Transportation Officials to keep updated on whether there will be any changes in funding.

And as news trickles out about Trump's new administration in the coming weeks, transportation is likely to take a back seat to talks about higher-profile appointments, such as secretary of state and attorney general.

"There's a lot of uncertainty about this administration," said Levinson. "But transportation spending doesn't seem to be the thing they should be worried about in this administration."