WASHINGTON (AP) — Racing toward a partial government shutdown, President Donald Trump's top envoys were dispatched to Capitol Hill as he dug in Friday in a standoff over his demand for billions of dollars in U.S.-Mexico border wall money.

Vice President Mike Pence, acting White House chief of staff Mick Mulvaney and senior adviser Jared Kushner arrived in late afternoon for a round of office calls, but there was no clear movement toward a deal with Democrats or Republicans to end the crisis.

The shutdown, scheduled for midnight, would disrupt government operations and leave hundreds of thousands of federal workers furloughed or forced to work without pay just days before Christmas.

At a White House bill signing, Trump said the government is "totally prepared for a very long shutdown."

Trump tried to pin the blame on Democrats for the possible shutdown, even though just last week he said he would be "proud" to shut part of the government in a fight for the wall, which was a major promise of his presidential campaign.

"This is our only chance that we'll ever have, in our opinion, because of the world and the way it breaks out, to get great border security," Trump said Friday at the White House. Democrats will take control of the House in January, and they oppose major funding for wall construction.

Trump convened Republican senators for a lengthy meeting at the White House, but the lengthy back-and-forth with the president did not appear to set a strategy for moving forward. A person granted anonymity because they were unauthorized to discuss the private session said the president would not get behind lower levels of funding the senators discussed.

"I was in an hour meeting on that and there was no conclusion," said Sen. Chuck Grassley of Iowa.

Senate Majority Leader Mitch McConnell returned to Capitol Hill saying lawmakers "had a good conversation about the way forward."

McConnell quickly set in motion a Senate procedural vote on a House Republican package that would give Trump $5.7 billion for the wall, but it was not expected to pass. At least one Republican, retiring Sen. Jeff Flake of Arizona, was opposed, saying he would resist wall money without broader immigration reforms, leaving even the procedural vote in doubt.

To underscore the difficulty, the Senate vote was stuck in a long holding pattern waiting for the return of senators who had already left town.

Senators were being recalled to Washington after having already approved a bipartisan package earlier this week that would continue existing border security funding, at $1.3 billion, but without new money for Trump's wall.

Amid the impasse, Pence and the others were dispatched to the Capitol to meet with Senate Minority Leader Chuck Schumer, who told them that Trump's demands for wall money would not pass the Senate, according to the senator's spokesman.

Schumer told Pence, Mulvaney and Kushner other offers to keep the government running with existing levels of border security funds remain on the table.

Pence and the others later walked across the Capitol to meet with House Speaker Paul Ryan.

Friday's voting dragged on as senators rushed back to town. Texas Sen. John Cornyn, the Senate's No. 2 Republican, said he returned to the Lone Star state on Thursday only to get back on an early Friday morning flight to Washington.

Democratic Sen. Brian Schatz flew all the way home to Hawaii, tweeting that he spent 17 minutes with his family, before returning on the 11-hour flight.

"Wheels down IAD ready to vote no on this stupid wall," Schatz tweeted Friday, referring to Dulles International Airport outside Washington.

The Senate was expected to reject the House measure because Democratic votes are needed and McConnell showed little interest in changing the rules — as Trump proposed — to allow a simple majority for passage.

One possibility was that the Senate might strip the border wall funds out of the package, pass it and send it back to the House. House lawmakers said they were being told to stay in town for more possible votes.

"The biggest problem is, we just don't know what the president will sign," said Flake.

Only a week ago, Trump insisted during a televised meeting at the White House he would take ownership of a shutdown over his border wall. "I will take the mantle. I will be the one to shut it down," he asserted.

But with the hours dwindling before the midnight deadline, Trump sought to reframe the debate and blame Democrats for the impasse that threatens hundreds of thousands of federal workers on the eve of the end-of-the-year holidays.

"Senator Mitch McConnell should fight for the Wall and Border Security as hard as he fought for anything. Later in the morning, not even waiting for a Senate vote, Trump tweeted that "the Democrats now own the shutdown!"

The White House said Trump would not go to Florida on Friday as planned for the Christmas holiday if the government were shutting down.

At issue is funding for nine of 15 Cabinet-level departments and dozens of agencies, including the departments of Homeland Security, Transportation, Interior, Agriculture, State and Justice, as well as national parks and forests.

Many agencies, including the Pentagon and the departments of Veterans Affairs and Health and Human Services, are funded for the year and would continue to operate as usual. The U.S. Postal Service, busy delivering packages for the holiday season, would not be affected because it's an independent agency.

Thursday night, the GOP-led House voted largely along party lines, 217-185, to attach the border wall money to the Senate's bill. House Republicans also tacked on nearly $8 billion in disaster aid for coastal hurricanes and California wildfires.

Both the House and Senate packages would extend government funding through Feb. 8, all but guaranteeing another standoff once Democrats take control of the House in the New Year.

"There are a lot of us who want to avoid a shutdown," said Kansas GOP Sen. Pat Roberts. "I've been through about five of them in my career. None of them have worked in terms of their intent."

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Associated Press writers Alan Fram, Kevin Freking, Mary Clare Jalonick and Jill Colvin in Washington contributed to this report.