Senate Democrats announced on Thursday that they would put off their upcoming holiday break and stay in Washington next week to press for passage of a bill pairing military assistance for Ukraine with a crackdown on migration at the U.S. border with Mexico, as lawmakers on both sides of the talks reported progress toward a compromise.
The move, announced by Senator Chuck Schumer of New York, the majority leader, was a bid by Democrats to intensify the pressure on Republicans to drop their opposition to the Ukraine funding bill, after House G.O.P. leaders left Washington for the year without acting on the matter. It also reflected fresh optimism among Senate negotiators who had been haggling over a border enforcement package that they were inching closer together — and a determination by Democrats to show the public that they were doing everything in their power to strike a bargain.
“If we believe something is important and urgent, we should stay and get the job done,” Mr. Schumer said on the Senate floor, calling on White House officials and senators in both parties to work through the weekend to strike a border deal. Whether or not they could, he added, there would be another vote next week on the $110.5 billion security package. Republicans blocked that measure last week because it lacked the immigration policy changes they sought.
Even if the Senate is able to reach agreement within days on one of the most intractable issues Congress has faced and push the Ukraine bill forward, the measure would still face an uphill battle. Speaker Mike Johnson, who is not involved in the border talks, threw cold water on the idea of quick action.
“The House will not wait around to receive and debate a rushed product,” he said in a statement on Thursday night.
And many Republican senators — including some of those closest to the negotiations — said they were skeptical that it was possible to make a deal before Christmas.
“It’s a tall order,” said Senator Thom Tillis, Republican of North Carolina. Other Republicans cast doubt on the notion that they would return at all next week.
In the absence of an agreement, White House officials and Democrats on Capitol Hill accused House Republicans of abandoning Ukraine at a critical time.
“They’re heading home for the holidays while Ukrainians are heading right back into the fight,” John Kirby, the spokesman for the National Security Council, said. The Ukrainians “need our help and they need it right now — not after the eggnog.”
Still, over the last few days, as White House aides and Alejandro N. Mayorkas, the homeland security secretary, joined the closed-door talks in the Senate over stricter border policies, there has been a growing sense that a deal might be possible. Negotiators have been discussing increased detention of migrants at the border and a policy known as expedited removal, which allows migrants to be deported swiftly before they are able to make asylum claims.
Those proposals have prompted a backlash from pro-immigrant lawmakers, who have warned Senate Democrats and the White House against making a deal to save Ukraine at the expense of migrants.
“They’re brutal and inhumane,” said Representative Pramila Jayapal, Democrat of Washington, said of some of the border enforcement proposals under discussion. “If we want to deal with immigration, then we should deal with it in a proper way, not as a ransom demand.”
But many Democrats seemed to have made their peace with the idea of stiff new immigration restrictions, effectively accepting the G.O.P.’s argument that Congress could no longer defer dealing with the border crisis.
“Changes have to be made in our policy at the border. What we currently see is unsustainable,” Senator Richard J. Durbin, Democrat of Illinois and the majority whip, told reporters, noting that “it’s inevitable if we’re going to change policy on the border there will be critics on the Democratic side.”
Negotiators said they would keep working through the weekend.
“We’re going to work as long as there’s daylight,” said Senator James Lankford, Republican of Oklahoma and the lead negotiator for the G.O.P.
“This is, lock everybody in a room over the weekend and see how far they can get,” said Senator Chris Van Hollen, Democrat of Maryland.
Because of the opposition within their own party, Democrats would likely need the support of at least 20 Republicans for any deal. Many are reluctant to back something they fear might fail in the House, where Republican leaders have said they want to see more restrictive border policies than are currently on the table in Senate negotiations.
Some G.O.P. senators warned Mr. Schumer not to try to jam a deal through the Senate just to meet a preholiday deadline.
“There is no chance that you can come to an agreement, draft a legislative proposal, get the text together and then actually give people sufficient time to read it,” Senator J.D. Vance, Republican of Ohio, said. If Mr. Schumer plows ahead with his plans, he added, “you’ll have a revolt on the Republican side.”
Zolan Kanno-Youngs contributed reporting.