Congressional leaders reached an agreement on overall spending levels to fund the federal government in 2024, a significant step toward averting a shutdown later this month. But political divisions on immigration and other domestic priorities could stall its progress. The deal is separate from bipartisan Senate negotiations that would pair new border security measures with additional funding for Israel and Ukraine. That proposal was expected to be released as early as this week, but a senator involved in the talks said on Monday that the timeline was “doubtful”. The details of this deal, negotiated by the Republican House speaker, Mike Johnson, and the Democratic Senate majority, Chuck Schumer, must still be worked out. Joe Biden praised the deal but some conservatives are unhappy, underscoring the fragile nature of the agreement with just days left to finalize it. What’s the deal? Congressional leaders agreed on a “topline” figure to finance the federal government in fiscal year 2024: $1.59tn. In a letter to colleagues over the weekend, Johnson said the spending levels include $886bn for the military and $704bn for non-defense spending. Johnson said Republican negotiators won “key modifications” as part of the deal, which he said will further reduce non-military spending by $16bn from a previous agreement brokered by Kevin McCarthy, then the House speaker, and Biden. Additionally, he noted that the overall spending levels were roughly $30bn less than a proposal the Senate had considered. The agreement rescinds roughly $6bn in unspent Covid relief funds and accelerates plans to slash by $20bn new funding that the Internal Revenue Service was supposed to receive under the Inflation Reduction Act, Johnson said. Congressional negotiators are now up against a tight deadline to write and pass 12 individual appropriations bills, an unlikely feat given the timeframe. Funding for roughly one-fifth of the government expires on 19 January, while the rest of the government remains funded until 2 February. Alternative options include a continuing resolution, known as a CR, or an all-in-one omnibus bill, both of which conservatives find unpalatable. How are leaders selling it? Biden said the agreement “moves us one step closer to preventing a needless government shutdown and protecting important national priorities”. “It reflects the funding levels that I negotiated with both parties and signed into law last spring,” Biden said in a statement. “It rejects deep cuts to programs hardworking families count on, and provides a path to passing full-year funding bills that deliver for the American people and are free of any extreme policies.” Democratic leaders cast the deal as a win. “When we began negotiations, our goal was to preserve a non-defense funding level of $772bn – the same level agreed to in our debt ceiling deal last June – and that $772bn was precisely the number we reached. Not a nickel – not a nickel – was cut,” Schumer said in a speech on the Senate floor on Monday. While Johnson touted several “hard-fought concessions” secured in the deal, he also acknowledged that not everyone in his caucus would be pleased by the agreement. “While these final spending levels will not satisfy everyone, and they do not cut as much spending as many of us would like, this deal does provide us a path to: 1) move the process forward; 2) reprioritize funding within the topline towards conservative objectives, instead of last year’s Schumer-Pelosi omnibus; and 3) fight for the important policy riders included in our House FY24 bills,” he wrote in the letter. Can it hold? Even if lawmakers can work at lightning speed to draft a dozen appropriations bills in time, several hurdles lie ahead. Johnson, who holds a narrow majority in the House, is already facing a revolt from conservatives in his caucus. Hours after the speaker announced a deal had been reached, the arch-conservative House Freedom Caucus railed against it. “It’s even worse than we thought. Don’t believe the spin,” it said. “This is total failure.” Several conservatives say they want to see Johnson attach strict new border security measures to any government funding deal, and some have signaled a willingness to shut down the government if those demands are not met. In an interview on Sunday, Elise Stefanik, the No 4 House Republican, did not rule it out as a course of action. “We don’t support shutting down the government,” Stefanik said. “But we must secure the border. We must secure the border. That’s where the American people are. We’re losing our country in front of our very eyes.” Schumer said Democrats would balk at the inclusion of any “poison pill” amendments. “If the hard right chooses to spoil this agreement with poison pills, they’ll be to blame if we start careening towards a shutdown,” he said on Monday. “And I know Speaker Johnson has said that nobody wants to see a shutdown happen.” But Johnson is under pressure from the far right, and he knows his job could be on the line. Conservatives moved to oust his predecessor from the speakership after McCarthy struck a deal with Democrats to preserve spending levels and avert a government shutdown.