WASHINGTON — The Senate failed Wednesday to begin debate on President Joe Biden’s national security package, with Republicans unifying to filibuster it due to a lack of immigration limits that they have demanded be a condition for winning their support.

The vote was 49-51, with Republicans voting against moving forward with the bill, along with Sen. Bernie Sanders, I-Vt., who caucuses with Democrats. Sanders has said he opposes giving aid to Israel unconditionally unless Israeli Prime Minister Benjamin Netanyahu’s government changes its practice, which he has called “immoral” and “in violation of international law.”

The failed vote leaves U.S. aid to Ukraine and Israel on life support on Capitol Hill, even as Biden makes a dire plea for approving it to stop Russia from conquering Ukraine.

“This cannot wait. … We cannot let [Russian President Vladimir] Putin win,” Biden said, accusing “extreme” Republicans of “playing chicken” with the package by demanding “partisan” border policies.

“Do they really want a solution?” he asked. “I am willing to make significant compromises on the border.”

Senate negotiations on border security and immigration policy hit a breaking point last Friday amid irreconcilable differences between Republicans, who want to take aggressive steps to stem the flow of migration, and Democrats, who accuse the GOP of pushing radical changes that would shut off legal pathways to the United States.

The talks had been led by Sen. James Lankford, R-Okla., and Sen. Chris Murphy, D-Conn., who in recent days have been unable to agree on whether they’re still even negotiating.

Lankford left the vote saying, “This is not the end.”

The Republican said Biden’s remarks were a step in the right direction.

“I see that as a significant sign that he understands, hey, this is a holistic package. We’ve been talking about national security. It’s got to all be there,” he said, adding that he’s in touch with White House staff about it. “We’ve got to get back in the room and talk through — how do we actually land the plane?”

“We understand there has to be a bipartisan agreement over here,” Lankford continued. “We’re not delusional to think this is going to be a Republican-only bill” with a Democratic-led Senate and White House and a narrow GOP majority in the House.

Before the vote, Senate Majority Leader Chuck Schumer reiterated his offer to Republicans to craft a border amendment of their choosing and vote on it as part of the bill at a threshold of 60 votes. He said the package represents “a moment of truth for the Senate, for the country, for the fight for democracy and western values.”

When all senators had voted on Wednesday, the outcome was 50-50, but Schumer changed his vote to a no to preserve his procedural option to bring up the bill again.

Even if the Senate reaches a deal and passes it, there’s no guarantee it will pass muster in the House, where Speaker Mike Johnson, R-La., is under pressure from conservative hard-liners to insist on a far-reaching border and immigration package, known as H.R. 2, that Democrats say is a nonstarter.

In the Senate, many Republicans say they favor Ukraine funding but they see migration issues in the U.S. as a bigger problem.

“I’m more worried about our border than Ukraine,” said Sen. Lindsey Graham, R-S.C.

Sen. John Cornyn, R-Texas, said it’s ultimately going to take White House involvement with the Senate’s top leaders to get a deal done.

“I like Senator Murphy and he and I’ve done some good work together, but I think he was never going to be able to negotiate the kind of meaningful substantive policy changes because Schumer would never allow it,” Cornyn said. “So this has got to take place between the big guy at the White House, who actually said some positive things today, and Senator McConnell and the Speaker.”

Sen. Tim Kaine, D-Va., said he still believes Congress will get the package done by the holidays.

Murphy made clear Wednesday that he remains frustrated by Republicans linking the aid package to an immigration dispute.

“I don’t know, I’m reconsidering my whole position on Ukraine funding. I think that I’m going to demand that we pass an assault weapons ban or I won’t fund Ukraine,” he said. “I guess that’s how things get done around here.”

The Connecticut Democrat called Biden’s remarks “an accurate representation of the White House position — the White House is willing to endorse and implement changes.”

“But they can’t implement changes that can’t pass Congress,” he said. “And right now, the ideas that Republicans have proposed cannot pass Congress, period, stop.”