WASHINGTON — President Donald Trump stalked out of his negotiating meeting with congressional leaders Wednesday — “I said bye-bye,” he tweeted soon after — as efforts to end the 19-day partial government shutdown fell into deeper disarray over his demand for billions of dollars to build a wall on the U.S.-Mexico border. Hundreds of thousands of federal workers now face lost paychecks on Friday.

The president is to visit the border in person on Thursday, but he has expressed his own doubts that his appearance and remarks will change any minds.

The brief session in the White House Situation Room ended almost as soon as it began.

Democrats said they asked Trump to reopen the government but he told them if he did they wouldn’t give him money for the wall that has been his signature promise since his presidential campaign two years ago.

Republicans said Trump posed a direct question to House Speaker Nancy Pelosi: If he opened the government would she fund the wall? She said no.

Senate Democratic leader Chuck Schumer said Trump slammed his hand on the table and walked out. Republicans said Trump, who passed out candy at the start of the meeting, did not raise his voice and there was no table pounding.

One result was certain: The shutdown plunged into new territory with no endgame in sight. The Democrats see the idea of the long, impenetrable wall as ineffective and even immoral, a terrible use of the $5.7 billion Trump is asking. He sees it as an absolute necessity to stop what he calls a crisis of illegal immigration, drug-smuggling and human trafficking at the border.

“The president made clear today that he is going to stand firm to achieve his priorities to build a wall — a steel barrier — at the southern border,” Vice President Mike Pence told reporters afterward.

That insistence and Trump’s walking out were “really, really unfortunate,” said Schumer.

Trump had just returned from Capitol Hill where he urged jittery congressional Republicans to hold firm with him. He suggested a deal for his border wall might be getting closer, but he also said the shutdown would last “whatever it takes.”

He discussed the possibility of a sweeping immigration compromise with Democrats to protect some immigrants from deportation but provided no clear strategy or timeline for resolving the standoff, according to senators in the private session. He left the Republican lunch boasting of “a very, very unified party,” but GOP senators are publicly uneasy as the standoff ripples across the lives of Americans and interrupts the economy.

Trump insisted at the White House “I didn’t want this fight.” But it was his sudden rejection of a bipartisan spending bill late last month that blindsided leaders in Congress, including Republican allies, now seeking a resolution to the shutdown.

GOP unity was being tested further late Wednesday with the House voting on a bipartisan bill to reopen one shuttered department, Treasury, to ensure that tax refunds and other financial services continue. Republicans were expected to join Democrats in voting, defying the plea to stay with the White House.

Ahead of his visit to Capitol Hill, Trump renewed his notice that he might declare a national emergency and try to authorize the wall on his own if Congress won’t approve the money he’s asking.