On Tuesday, Senate leaders spoke in a measured, almost rehearsed manner as Congress inched closer to an increasingly probable later this week, propelled by a political divide over immigration enforcement and the funding of the Department of Homeland Security.

With funding for a significant portion of the federal government set to expire at midnight on Friday, Republicans and Democrats remain at an impasse over a vast six-bill appropriations package that the House sent to the Senate and which includes funds for Homeland Security. In the wake of Saturday’s involving federal immigration agents, Democrats are demanding changes to that section of the bill—and indicating they are ready to let funding lapse if those demands are ignored.

Addressing the Senate floor, Minority Leader Chuck Schumer, a New York Democrat, called on Republicans to divide the appropriations package, pass the five bills with bipartisan support, and send the Homeland Security measure back for revision. “The Senate must not pass the DHS budget as it is currently written,” Schumer stated. “It must be reworked to rein in and overhaul ICE to ensure public safety.”

Senate Majority Leader , a South Dakota Republican, urged Democrats to “find a way forward that will prevent an unnecessary shutdown and not put full funding for key agencies like FEMA and the Coast Guard at risk.” In the Senate, Republicans can’t pass a funding bill without some Democratic support, giving the minority party leverage it lacks in the House.

The standoff has made a partial shutdown more likely due to the process mechanics and the Congressional calendar. If Senate Democrats succeed in removing the Homeland Security funding or making any other changes to the bill, the revised package would have to be sent back to the House for approval. But the House is in recess until next week, making it nearly impossible to avoid a lapse if changes are made unless Speaker Mike Johnson agrees to recall House lawmakers to Washington. The House Freedom Caucus, a group of hard-right Republicans in the lower chamber, also on Tuesday that they might derail the procedural votes needed to advance any alternative funding package.

“I think it’s always a risky endeavor if you have to send it back to the House,” Thune told reporters on Tuesday. “No one knows what will happen over there.”

The political pressure escalated after federal agents killed Alex Pretti, a 37-year-old intensive care unit nurse and U.S. citizen, during an immigration operation in Minneapolis over the weekend—the second fatal shooting involving immigration agents in the city this month. This incident has energized Democrats, who are facing intense calls from their base to tackle what they describe as unbridled, militarized enforcement by Immigration and Customs Enforcement.

While Schumer has yet to release his caucus’ full list of demands, Democrats have said they are pushing for a series of changes to the Homeland Security bill, including requirements that immigration agents obtain judicial warrants for arrests, identify themselves during operations, cooperate with state and local investigations, and accept stricter limits on the scope of their enforcement activities. Several of these ideas had been circulating earlier in the year but gained new urgency after the shootings. Democrats have rejected suggestions that they accept actions by the Trump White House that would address their immediate concerns without shutting down the government.

“If Leader Thune agrees to split the bills just as Speaker Johnson split them in the House and puts the five on the floor, I’m confident they will pass through the chamber and we will have funded 96% of the federal government,” Schumer said on Tuesday. If Thune insists on proceeding with the full package, Schumer warned, “he will ensure yet another unnecessary government shutdown this Friday.”

But Republicans reject the idea of reopening months of bipartisan negotiations and argue that Democrats are going back on a deal their own appropriators helped draft, which also passed the House last week, before the shooting in Minneapolis. They also maintain that removing Homeland Security funding would have more far-reaching consequences than Democrats acknowledge, potentially harming agencies like the Federal Emergency Management Agency and the Coast Guard, which are within the department.

Yet the practical effects of a shutdown on immigration enforcement are than the political rhetoric implies. Even if Homeland Security funding lapses, ICE operations would almost certainly continue because the agency received tens of billions of dollars last year through President Donald Trump’s sweeping tax and spending law, giving it sufficient resources to sustain enforcement activities even during a shutdown.

Still, a shutdown would have repercussions across other parts of the government funded by the six-bill package, including the Pentagon and agencies responsible for transportation, housing, and health programs. Many federal workers would be required to keep working without pay, while others would be furloughed.

The White House has urged Congress to pass the package as written, and Republicans say Democrats would bear the political blame for blocking a bipartisan agreement. But Democrats argue that the responsibility lies with the majority.

“The solution should come from Congress,” Schumer said. “The public can’t trust the Administration to do the right thing on its own.”

But with time running out, even senators eager to avoid another shutdown acknowledge that the chances of finding a way out before Friday night are dwindling.