White House and congressional negotiators agreed Monday evening to fund the Department of Homeland Security along with nearly three-quarters of the federal government — starting a sprint on Capitol Hill to pass the legislation before a government shutdown deadline this weekend.

The agreement, the details of which are yet unclear, may not have come in time to prevent vast swaths of the government, including the Homeland Security, Defense and State departments, from at least partially shuttering just after midnight Saturday. The House, where the measure will originate, requires 72 hours’ notice before voting on legislation. The Senate requires 30 hours of debate, unless all 100 senators give consent to move faster. The bills were not yet released by Monday evening and may take more time to finalize.

The result could be a brief shutdown over the weekend while House Speaker Mike Johnson (R-La.) and Senate Majority Leader Charles E. Schumer (D-N.Y.) scramble to convince members to vote hastily. Already one group of hard-line House Republicans has urged colleagues not to support the measure without harsh new immigration and border security policies. And one Democratic senator has signaled he could slow the bill’s progress without a separate deal on emergency funding for Ukraine.

The agreement was confirmed by three people with knowledge of the talks, which had dragged on between representatives for Johnson and President Biden through the weekend. The people spoke on the condition of anonymity to discuss the fragile arrangement.

The legislation rolls together the remaining six appropriations bills, five of which had been completed for days. The Homeland Security measure, though, became a proxy for Republican and Democratic warring over immigration and border policy.

Lawmakers might be able to wrap up the spending bills not long after the deadline, blunting the impact of a partial shutdown that mostly takes place at night or on a weekend. But a prolonged closure could have cascading effects on the government and economy. More than half of IRS employees would face furloughs at the height of tax filing season. The roughly 1.3 million active-duty U.S. military service members would remain on the job without pay. So would Transportation Security Administration screeners, many of whom called in sick in protest during a previous shutdown, sparking nationwide travel delays.

The border disagreements have clouded the overall funding picture on Capitol Hill, ensnaring legislation on annual spending bills, or appropriations, and national security priorities in Europe, the Middle East and Indo-Pacific.

Former president Donald Trump’s rhetoric around the subject — he helped kill a bipartisan compromise on border security last month and said Sunday that some undocumented immigrants were “not people” and were “animals” — has fueled distrust at the bargaining table. Johnson and other leading Republicans have endorsed the former president and are said to consult with him on immigration policy.

The archconservative House Freedom Caucus encouraged colleagues to reject any annual spending, or appropriations, package that emerges from negotiations if it does not roll back significant Biden border policies or falls short of GOP priorities to reinstate harsh Trump-era immigration restrictions. The group’s members were unlikely to vote for any funding package to begin with, though, as many have deep disagreements with Johnson on spending amounts.

“At some point, border security has to be more than something aspirational that we simply message on,” the group wrote.

Border issues have complicated other funding measures, as well. Biden, Johnson and Schumer remain at an impasse about U.S. spending to support Ukraine, talks that have gone awry over Republican attempts to link the money to border security. Bipartisan talks in the Senate reached a sweeping immigration and border security compromise that was intended to satisfy GOP requests, but House lawmakers rejected it, as did Trump, and the Senate then voted it down last month.

Sen. Michael Bennet (D-Colo.) said in a statement last week that “Democrats should reject any House budget package that does not include support for Ukraine.” He has previously delayed Senate consideration of other funding bills for similar reasons.

The federal spending picture was not supposed to be this fraught. Biden and then-House Speaker Kevin McCarthy (R-Calif.) agreed last spring to suspend the nation’s debt ceiling in exchange for limiting federal spending in 2024. Some House Republicans detested that deal, which they hoped would generate deeper spending cuts. Disagreements over spending ultimately led a band of rebels to oust McCarthy from the speakership in October.

Johnson has abided by those spending amounts, though, and agreed with Schumer in January to a top-line spending figure — $1.7 trillion — for the rest of the fiscal year, which ends Sept. 30. Congress already passed, and Biden signed, the first leg of a government funding package worth $459 billion earlier this month. Negotiators had mostly agreed on measures to fund the rest of the federal government but were stuck on the Homeland Security provisions — which might have been difficult to pass on their own because of the political frenzy around immigration.

The number of migrants arriving along the Mexican border has fallen significantly since December, when authorities tallied 250,000 illegal entries, the highest monthly total ever.

A crackdown by Mexican authorities has slowed the pace of arrivals so far in 2024, but DHS officials expect a seasonal increase in illegal crossings this spring. That would put new strains on U.S. border agents and detention facilities.

The bipartisan bill that failed in the Senate last month included nearly $14 billion in supplemental funding for immigration and border security, including $6 billion for ICE detention and deportation operations. The funds would have allowed the agency to boost its detention capacity from 40,000 to 50,000 beds, according to administration officials.

Instead, ICE officials are facing a $700 million budget shortfall, and the agency has started drafting emergency plans to cut costs by releasing thousands of detainees. With fewer available detention beds, ICE has warned that it will also have to cut back on the number of people who cross the border illegally that it can accept from U.S. Customs and Border Protection.

That would increase the odds that migrants who enter the United States illegally will be released into the country, rather than detained and deported, regardless of whether they have strong asylum claims.

White House press secretary Karine Jean-Pierre told reporters Monday that the department has deported or returned more migrants during the past 10 months than during any year since 2013: “They have maximized their operations.”

But deportations have soared because record numbers of migrants are entering the United States. Authorities have tallied about 2 million illegal crossings along the Mexican border on average since Biden took office, the busiest stretch in history.

Asked if the White House became involved in the budget negotiations too slowly, Jean-Pierre pushed back.

“That is something that is the basic duty of Congress,” she said. “It is their job to keep the government open.”

Marianna Sotomayor contributed to this report.