Updated at 10:35 a.m. ET

The federal government may be in a partial shutdown, but the gears of a political blame game kept rolling Saturday morning. President Trump was tweeting at dawn, blaming Democrats for the lapse in government funding as the Senate failed to advance a four-week extension overnight.

Trump accused Democrats of choosing “unchecked illegal immigration” over the military, but Democrats say he has not kept his word on finding a deal to protect immigrants in the country illegally who arrived as children.

It’s an unprecedented situation, given that broad shutdowns usually happen in times of divided government. But this is the first time it’s happened with one party controlling both Congress and the White House.

Members of the House and Senate are reconvening in the Capitol on Saturday as they work to resolve the impasse. But it’s not clear what path there is to a compromise, as Republican leaders made clear they will not negotiate over immigration while the government is shut down.

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The House came back into session at 9 a.m. ET, before Republicans and Democrats headed for separate, closed-door caucus meetings to chart their paths forward. The Senate was set to return at Noon ET.

Senate Majority Leader Mitch McConnell, R-Ky., announced early Saturday that he will be offering an amendment to change the proposed funding bill from a four-week timeframe to three weeks, meaning it would extend funding through Feb. 8 instead of Feb. 16. But it does have any substantive changes on immigration or long-term spending, both issues that would be key to a longer resolution.

Early on Saturday morning, President Trump accused Democrats of playing “Shutdown politics.”

Maryland Sen. Chris Van Hollen, who leads the Senate Democrats’ campaign strategy, told NPR’s Weekend Edition that President Trump and Senate Minority Leader Chuck Schumer, D-N.Y., had a productive meeting at the White House on Friday. But after that, Van Hollen said, “The naysayers at the White House then got involved, and things went downhill from there,” referring to immigration hardliners in the administration.

Since most government offices won’t open again until Monday, there is time over the weekend for legislators to reach a compromise, and House members have been kept in Washington, D.C., in case that happens.

The three-week proposal before the Senate today has been championed by Sen. Lindsey Graham, R-S.C., since Friday evening. Graham had opposed the longer measure for four weeks of funding which passed in the House Thursday but failed in the Senate early Saturday morning, just after the shutdown took effect. Throughout the evening Friday, Graham’s proposal for a shorter time frame of stopgap funding seemed to be picking up steam with senators even as the chamber failed to pass the House measure and failed to reach any larger deal on a number of issues that have been under consideration relating to spending levels, immigration and border security.

As the shutdown took effect, talks among Senate leaders were still happening on the Senate floor after a procedural vote late Friday lacked the 60 yes votes needed to advance the House’s four-week funding bill.

Around 12:15 a.m. ET, McConnell voted no on the House measure, doing so for procedural reasons that allowed him to preserve the ability to bring up a substitute bill later. The final vote was 50-49, with Sen. John McCain, R-Ariz., absent from the vote.

The apparent congressional paralysis risked overshadowing the first anniversary of President Trump’s inauguration and capped off a year defined at times by chaos and frustration from both the White House and congressional Republicans despite their unified control of Washington.

And it comes after days of hurried negotiations to find a compromise failed, leading to finger-pointing from both parties eager to shift the blame to the other side.

Republicans and McConnell had been angling for a four-week continuing resolution, that included extending the popular Children’s Health Insurance Program (CHIP) for six years in an effort to entice Democrats to vote for the insurance program they want to fund.

But Democrats led by Schumer pushed to include an immigration measure that would include a pathway to citizenship for roughly 700,000 immigrants enrolled in the Deferred Action for Childhood Arrivals (DACA) program the Trump administration rescinded last year. Democrats wanted a pathway to citizenship for those roughly 700,000 immigrants who were in the country illegally after being brought here as children.

Republicans blamed Democrats for angling for the DACA legislative fix over keeping the government open, using the hashtag #SchumerShutdown and launching an accompanying website focused on Schumer.

Shortly before midnight, the White House released a statement blasting Democrats as “obstructionist losers.”

“Senate Democrats own the Schumer Shutdown. Tonight, they put politics above our national security, military families, vulnerable children, and our country’s ability to serve all Americans. We will not negotiate the status of unlawful immigrants while Democrats hold our lawful citizens hostage over their reckless demands. This is the behavior of obstructionist losers, not legislators,” White House press secretary Sarah Sanders said. “When Democrats start paying our armed forces and first responders we will reopen negotiations on immigration reform. During this politically manufactured Schumer Shutdown, the President and his Administration will fight for and protect the American people.”

Trump has canceled plans to travel to his Mar-a-Lago resort in Florida over the weekend, where he was set to have a gala fundraiser Saturday to commemorate his inauguration one year ago.

Just after midnight, McConnell took the Senate floor to put fault on Democrats for not backing the House bill and averting a shutdown.

“What we have just witnessed on the floor was a cynical decision to shove aside millions of Americans for the sake of irresponsible political gains,” the GOP leader said. “A government shutdown was 100 percent avoidable, completely avoidable. Now it is imminent all because Senate Democrats chose to filibuster a noncontroversial funding bill that contains nothing — not a thing — that they do not support.”

However, the hashtag #TrumpShutdown was also trending on Twitter late Friday night, and Democrats believe that it’s Republicans who will end up shouldering the majority of blame from the public given the GOP controls both Congress and the White House.

Trump appeared to complicate efforts to reach a compromise over the past weeks, at first signaling he would sign any immigration deal but then rejecting a bipartisan proposal, bending to his conservative, hardline base and insisting any deal had to have funding for his trademark border wall. And negotiations further stalled after Trump reportedly used a vulgarity in questioning why the U.S. should welcome immigrants from Africa instead of places like Norway. (Trump has denied that he used that language.)

Schumer took to the Senate floor immediately after McConnell early Saturday and said that when he met with Trump at the White House Friday, he had even put the border wall on the negotiating table in order to reach a compromise on DACA. But “even that was not enough to entice the president to finish the deal,” Schumer said, accusing Trump and Republicans of “rooting for a shutdown” which would “crash entirely” on the president’s shoulders.

“What happened to the president who asked us to come out with a deal and promised he’d take heat for it? What happened to that president? He backed off at the first sign of pressure,” Schumer said. “The same chaos, the same disarray, the same division and discord on the Republican side that’s been in the background of these negotiations for months unfortunately appears endemic.”

Polling released Friday from both Washington Post/ABC News and CNN found that most Americans would blame Trump and Republicans over Democrats in the event a shutdown occurred. However, CNN also found a majority said approving a budget deal was more important than finding a way to advance DACA.

As NPR’s Brian Naylor reported, if the shutdown continues, essential services will continue and essential workers would remain on the job, though unpaid. Active duty military will stay in service, along with post offices. In a change from the last time the government shut down in October 2013, the Interior Department announced it will work to keep national parks open and “as accessible as possible.”

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