By David Morgan and Richard Cowan
WASHINGTON (Reuters) -Bipartisan U.S. Senate talks on a border security deal that some have set as a condition for further Ukraine aid have hit a critical point, lawmakers said on Thursday, though the chamber's top Democrat said the negotiators would continue to push forward.
A small group of senators has spent months trying to iron out an agreement to address the flow of migrants across the U.S.-Mexico border. But the effort has recently encountered growing opposition among Republicans aligned with Donald Trump, the frontrunner for their party's presidential nomination.
"We're at a critical moment, and we've got to drive hard to get this done. And if we can't get there, then we'll go to Plan B," Senator John Thune, the chamber's No. 2 Republican, told reporters in the U.S. Capitol.
"For now, at least, there are still attempts being made to try and reach a conclusion that would satisfy a lot of Republicans," Thune added.
A source familiar with the talks said negotiators were trying to "revive" the effort by altering the legislation to bolster its appeal to Senate conservatives.
"I am glad that now negotiations are continuing to move forward. Of course there are still issues that must be settled, but negotiators will work all weekend in an effort to get this done," Senate Democratic leader Chuck Schumer said.
Senate Republican leader Mitch McConnell and other top party members, including Thune, want a border deal that can win support from most Senate Republicans, in hopes of prompting the Republican-controlled House of Representatives to take up the measure combining border security with aid for Ukraine, Israel and Taiwan.
House Republicans have urged Republican Speaker Mike Johnson to accept only the provisions of partisan border legislation called HR-2, which Democrats reject as draconian.
McConnell has been the most prominent Republican advocate for additional U.S. aid to Ukraine to help it fight off Russia's invasion, even as a growing number of his party in the House and Senate express skepticism about the value of spending more to help an ally. It was not clear what path McConnell might take on foreign aid if a border deal failed.
But Republicans aligned with Trump have become more voluble in their skepticism since the former president took to social media to warn against any deal that fails to deliver everything Republicans want to shut down border crossings.
The White House has said there was no reason for bipartisan border talks in the Senate not to continue.
"We need to come together on (a) common sense compromise on border measures and border policy and border resources. And we still are hopeful that that can happen," White House spokesperson Olivia Dalton said.
A DEAL NEXT WEEK?
Punchbowl News reported that McConnell told Republicans in a private meeting that the time and political will to pass a bipartisan border deal were running out, and that Republicans should not undermine Trump's intention to focus his White House campaign on immigration.
But Senator Thom Tillis, a North Carolina Republican who attended the meeting and has been involved in some of the negotiations, said it was "patently false" that McConnell had changed course.
McConnell emphasized his commitment to a border deal and Ukraine aid during a Republican lunch on Thursday, according to lawmakers who attended.
"He's not going to let political considerations of any campaign stand in the way of his support," Republican Senator Mitt Romney said.
McConnell did not comment to reporters as he exited the lunch.
More than half of the 49 Senate Republicans have endorsed Trump, and many want the conference to reflect the former president's positions on major issues, including the border.
"Republicans should pay very close attention to the position that President Trump adopts regarding the border," said Republican Senator Bill Hagerty.
Senator Chris Murphy, the Democratic lawmaker in the negotiations, said Republicans will have to decide whether to accept a border deal that has yet to be finalized.
"We have produced the compromise that they (Republicans) asked for, with the chosen negotiator that they appointed, and it is now up to them as to whether they want to accept the agreement," the Connecticut lawmaker told reporters.
Another negotiator, independent Senator Kyrsten Sinema, told KGUN-TV in Tucson that she expects the text of a deal to be released "early next week."
Republican Senator Todd Young said it would be a mistake to give up on the issue now by taking negotiations off the table to "pay fealty to short-term considerations."
"I don't believe we should take this off the table, certainly not to clear the way for a clean campaign debate season," Young told reporters. "Let's get something consequential done for the American people."