WASHINGTON (AP) — A bitterly divided Congress hurtled toward a government shutdown this weekend in a partisan stare-down over demands by Democrats for a solution on politically fraught legislation to protect about 700,000 younger immigrants from being deported.

Democrats in the Senate have served notice they will filibuster a four-week, government-wide funding bill that cleared the House Thursday evening, seeking to shape a subsequent measure but exposing themselves to charges they are responsible for a looming shutdown.

Republicans controlling the narrowly split chamber took up the fight, arguing that Democrats were holding the entire government hostage over demands to protect “dreamer” immigrants brought to the country illegally as children.

“Democratic senators’ fixation on illegal immigration has already blocked us from making progress on long-term spending talks,” said Senate Majority Leader Mitch McConnell, R-Ky. “That same fixation has them threatening to filibuster funding for the government.”

President Donald Trump entered the fray early Friday morning, mentioning the House-approved bill on Twitter, adding: “Democrats are needed if it is to pass in the Senate – but they want illegal immigration and weak borders. Shutdown coming? We need more Republican victories in 2018!”

The White House said Friday that Trump will not leave for a planned weekend in Florida unless a funding bill passes. Trump had been set to leave Friday afternoon to celebrate the one-year anniversary of his inauguration at Mar-a-Lago.

In the House, Republicans muscled the measure through on a mostly party-line 230-197 vote after making modest concessions to chamber conservatives and defense hawks. House Speaker Paul Ryan immediately summoned reporters to try to pin the blame on top Senate Democrat Chuck Schumer of New York.

A test vote on a filibuster by Senate Democrats appeared likely before the shutdown deadline of Friday at midnight. Schumer was rebuffed in an attempt to vote Thursday night.

“We can’t keep kicking the can down the road,” said Schumer, insisting on more urgency in talks on immigration. “In another month, we’ll be right back here, at this moment, with the same web of problems at our feet, in no better position to solve them.”

The measure would be the fourth stopgap spending bill since the current budget year started in October. A pile of unfinished Capitol Hill business has been on hold, first as Republicans ironed out last fall’s tax bill and now as Democrats insist on progress on immigration. Talks on a budget deal to ease tight spending limits on both the Pentagon and domestic agencies are on hold, as is progress on a huge $80 billion-plus disaster aid bill.

House GOP leaders sweetened the pending stopgap measure with legislation to extend for six years a popular health care program for children from low-income families and two-year delays in unpopular “Obamacare” taxes on medical devices and generous employer-provided health plans.

A shutdown would be the first since 2013, when tea party Republicans — in a strategy not unlike the one Schumer is employing now — sought to use a must-pass funding bill to try to force then-President Barack into delaying implementation of his marquee health care law.

Democrats want a deal to protect around 700,000 immigrants from deportation who arrived in the U.S. as children and have stayed here illegally. Trump has ended an Obama-era program providing those protections and given Congress until March to restore them, and he and Republicans want any immigration deal to include money for the president’s promised wall along the Mexican border and other security measures.

Congress must act by midnight Friday or the government will begin immediately locking its doors. Though the impact would initially be spotty — since most agencies would be closed until Monday — the story would be certain to dominate weekend news coverage, and each party would be gambling the public would blame the other.

In the event of a shutdown, food inspections, federal law enforcement, airport security checks, and other vital services would continue, as would Social Security, other federal benefit programs and military operations. But federal workers wouldn’t be paid.

Sen. Ted Cruz, R-Texas, speaks to reporters as he walks towards the Senate as Congress moves closer to the funding deadline to avoid a government shutdown on Capitol Hill in Washington, Thursday, Jan. 18, 2018. (AP Photo/Andrew Harnik)