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(WASHINGTON) — Senators at the Capitol adjourned for the holidays Saturday afternoon without finding a way to negotiate an end to the government shutdown over President Trump’s demand for billions of dollars for a U.S.-Mexico border wall.

Senate Majority Leader Mitch McConnell, R-Kentucky, announced on the floor that the Senate will meet again on Thursday at 4 p.m.

He left open the possibility, however, that senators would return if a deal is struck between Republicans, Democrats and Trump.

“If an agreement is reached, we’ll come back and pass it,” McConnell, who is headed back to Kentucky, said. “Listen, anything can happen. We’re pulling for an agreement. If it gets 60 votes in the Senate, and the majority in the House.”

The abrupt ending capped a day of lawmakers negotiating and hoping to put an end to the government shutdown, which officially went into effect at midnight. The impasse between Democrats and the president has left hundreds of thousands of federal workers — 420,000 working without pay, and another 380,000 furloughed — out of work days before the holidays.

With Christmas Eve and Christmas early this week, the shutdown is expected to last until at least the middle of next week.

Right before the senators adjourned for the day, Trump tweeted that the “illegal activity at our Southern Border real and will not stop until we build a great Steel Barrier or Wall.”

The crisis of illegal activity at our Southern Border is real and will not stop until we build a great Steel Barrier or Wall. Let work begin!

— Donald J. Trump (@realDonaldTrump) December 22, 2018

“Let work begin!” he wrote.

He later tweeted that he won the 2016 election “based on getting out of endless & costly foreign wars & also based on Strong Borders which will keep our Country safe.”

“We fight for the borders of other countries, but we won’t fight for the borders of our own!” he wrote.

Earlier on Saturday, a senior administration official told reporters on a conference call that the president continued to push for $5 billion as his goal, although that may be the president’s opening bid rather than a non-negotiable.

“We have continued to put forth what we think is an important expectation for these negotiations, which is $5 billion in border security,” the senior administration official said.

McConnell said he hit the “pause button” until the president and Democrats could reach a deal.

Roughly 25 percent of the federal government -– and agencies including the State Department, IRS, Justice Department and Department of Homeland Security — shut down at midnight after Trump said he wouldn’t sign a funding bill that didn’t include $5 billion in funds for the construction of a wall.

Trump’s position seemed to harden after conservative allies on Capitol Hill and right-wing media began criticizing him this week. The president then prompted the House to add billions to a bipartisan Senate bill on Thursday and send the measure back to the Senate, where it lacked the support needed to clear the 60-vote threshold.

Democrats reiterated Saturday that they wouldn’t accept funding for the border wall, suggesting little progress had been made in preliminary discussions between congressional leadership and White House officials.

“President Trump, if you want to open the government, you must abandon the wall,” Senate Minority Leader Chuck Schumer, D-NY, said Saturday.

Earlier in the day, Trump had lunch with Vice President Mike Pence and a group of conservative House and Senate Republicans supportive of his border wall fight.

Afterward, Pence made his way back to the Capitol for a meeting with Schumer, whose aide told ABC News he expects to get a readout of what was discussed at lunch.

The meeting between the two comes at the White House’s request, according to the aide in Schumer’s office.

Schumer intended to remind the vice president that any proposal with funding for the wall cannot pass the Senate, the aide said.

Democratic Whip Steny Hoyer, D-Maryland, told ABC News that Trump “refuses to compromise.”

“When you don’t have the votes,” he added, “you need to compromise.”

Should Trump and congressional leaders fail to reach an agreement, Hoyer said Democrats were ready to pass a funding bill through the House when they take control of the chamber in January.

Much of the Capitol was stuck between that transition Saturday because of the shutdown. Boxes and Christmas decorations were stacked outside of offices that were scheduled to be swapped between Republican and Democratic House leaders before the shutdown.

House Speaker Paul Ryan was seen entering his leadership office Saturday morning with an overnight bag. The retiring speaker, who spends his nights in Washington in his office, had been evicted from his congressional office in the Longworth House Office Building.

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