Senate Democrats threatened to block passage of a four-month spending bill that would keep the government running. Here's why. (Peter Stevenson/The Washington Post)

Senate Democrats are threatening to force a brief government shutdown this weekend to pressure Republicans to support policies they say match promises President-elect Donald Trump made on the campaign trail to help coal country and boost American manufacturers.

Government funding is set to run out at the end of Friday and lawmakers are considering a stopgap spending bill that would keep federal agencies funded through April 28. The angry Democrats are not threatening to block the spending measure, but to threaten to miss the Friday deadline in hopes they can entice Republicans into further negotiations.

The tension over the spending bill is a sign of the possible scrambled alliances to come when Trump is inaugurated and how they could prove to be a headache for Republican leaders.

The senator fighting to have more generous medical and pension benefits for retired coal miners included in the spending bill is West Virginia Democrat Joe Manchin III, whose state Trump won handily, in part, by promising to renew the coal industry. Manchin is one of several red state Democrats expected to face a tough reelection bid in 2018. He is set to meet with the president-elect at Trump Tower on Friday morning and it’s unclear whether they’ll discuss the issue. The Democratic senator has been floated as a possible member of Trump’s cabinet.

“I want to shut her down,” Manchin said Wednesday about the government, pointing to his anger over concerns about the miner provisions. “I mean this is ridiculous . . . You can’t throw 16,000 people out.”

About 12,500 former union miners and their families have been told their health benefits will lapse come Jan. 1, and an additional 10,000 are in danger of losing benefits at a later date. Many are also facing potential cuts to their retirement benefits due to declining coal companies being unable to make required contributions to pension funds.

Manchin is demanding a vote on an amendment to extend miners’ medical benefits for one year. The spending bill includes a four month extension, which critics of the proposal say is inadequate.

Democrats are playing up Trump’s support for coal country as they try to pressure Republicans.

They said health care for miners has bipartisan support and would easily pass if Republican leaders would allow a vote on the measure. Incoming Senate Minority Leader Charles E. Schumer (D-N.Y.) told reporters the issue could unite Democrats and Trump.

“I hope our new president-elect, who talked and got to know the miners, will speak out,” Schumer said. “We don’t care about partisanship.”

Sen. Heidi Heitkamp (D-N.D.) called out Trump by name as she left a Thursday meeting between Senate Minority Leader Harry M. Reid (D-Nev.) and several of the Democrats who represents states where Trump won.

“We think there has been a renewed interest in these kind of issues with president-elect Donald Trump,” said Heitkamp who recently met with him in New York. “We’re hopeful that we’ll be able to get relief and be able to deliver a Christmas present to some of the most sympathetic working people in America.”

Senate Democrats also want funding for the “Buy American” program included in a water resources bill that is slated to come up for a Senate vote after the spending bill is complete. Republicans have been willing to support the provision as part of temporary spending bills but resisted including it in more permanent legislation like the water bill.

That tension puts Republicans at odds with Trump, who backed the concept at a rally last week.

“Whether it’s producing steel, building cars or curing disease, we want the next generation of innovation and production to happen right here in America and right here in Ohio, right?” Trump said in Cincinnati.

One Republican, Sen. Shelley Moore Capito of West Virginia, said Thursday she will oppose the stopgap unless the miners provision is addressed. Six other GOP senators signed a letter last month supporting a long term fix to the health care issue.

House Republicans have shown little interest in negotiating on the issue.

AshLee Strong, a spokeswoman for House Speaker Paul D. Ryan (R-Wis.), said the House is set to leave Washington after voting Thursday afternoon and does not plan to consider any further legislation until January

The House on Thursday passed the spending bill on a 326 to 96 vote.

The Senate will now need to vote on the legislation by the end of Friday to avert a government shutdown. But there would need to be unanimous consent to take up the bill in time to meet that deadline and Democrats are threatening to withhold their support for such a procedural move. The Senate would still be able to vote Sunday to pass the appropriations measure without this consent, but it would force a roughly one-day government shutdown.

The effort by Democrats to stick together to force action for miners and steelworkers has also sparked intraparty tensions — specifically, because the spending bill and an accompanying water projects package include funding to address the water crisis in Flint, Mich. — which has been a priority for Democratic lawmakers for more than a year.

“Here’s the thing: It feels like there’s always a reason not to do Flint,” said Rep. Daniel Kildee (D-Mich.), who urged his Senate colleagues to pass both bills. “People who live in Flint and places like Flint get kind of accustomed to being left behind. They get kind of accustomed to having other priorities supersede theirs. And you know what? Enough of that . . . Their interests have to sometimes come before other important priorities.”