WASHINGTON — White House and Senate negotiators dug in Sunday laboring to reach a U.S. border security deal that would unlock President Joe Biden’s request for billions of dollars worth of military aid for Ukraine and other national security needs before senators leave town for the holiday recess.

The Biden administration, which is becoming more deeply involved in the talks, is facing pressure from all sides over any deal. Negotiators had hoped to reach a framework by the weekend, but that’s highly unlikely. Republican leaders signaled that without bill text, an upcoming procedural would likely fail.

The talks come as Donald Trump, the Republican presidential front-runner in 2024, delivered alarming anti-immigrant remarks about “blood” purity over the weekend, echoing Nazi slogans of World War II to cheers at a political rally.

“They’re poisoning the blood of our country,” Trump said about the record numbers of immigrants coming to the U.S. without immediate legal status.

Speaking in the early-voting state of New Hampshire, Trump, drew on words similar to Adolf Hitler’s “Mein Kempf” as the former U.S. president berated Biden’s team over the flow of migrants. “All over the world they’re pouring into our country,” Trump said.

Throughout the weekend, senators and top Biden officials, including Homeland Security Secretary Alejandro Mayorkas, have been working intently behind closed doors at the Capitol to strike a border deal, which Republicans in Congress are demanding in exchange for any help for Ukraine, Israel and other national security needs.

“One step at a time,” said Sen. Chris Murphy, D-Conn., as he and Sen. Kyrsten Sinema, the Arizona independent, headed into talks.

The senators have insisted they are making progress, as they narrow on proposals to limit migrants from entering at the U.S.-Mexico border, but other influential lawmakers are doubtful any deal can be approved by Congress before year’s end.

Republican Sen. Lindsey Graham of South Carolina said senators don’t want to be “jammed” by a last-minute compromise reached by negotiators.

“We’re not anywhere close to a deal,” Graham, whose staff has joined the talks, said Sunday on NBC’s “Meet the Press.”

Graham predicted the deliberations will go into next year. He was among 15 Republican senators who wrote to GOP leadership urging them to wait until the House returns Jan. 8 to discuss the issue.

Top GOP negotiator Sen. James Lankford of Oklahoma and Senate Republican Leader Mitch McConnell also signaled in their own letter Sunday that talks still had a ways to go, and that this week’s planned procedural vote would likely fail.