WASHINGTON — Congress is bracing this month for another round of bitter spending battles over President Trump’s promised border wall and his immigration agenda, with only three weeks remaining before the government runs out of money.
With the memory of the nation’s longest government shutdown still fresh in their minds, White House officials and congressional leaders are pushing for a temporary agreement in the coming weeks to hold off a funding breach and allow more time to resolve the thorniest issues. But with senators set to convene on Tuesday for only the second time this year to debate the entire federal spending picture, the race to reconcile at least a fraction of the 12 necessary bills is particularly charged, even by the usual standards of the divided Congress.
“If both parties want to reach an agreement, we will reach an agreement,” Representative Nita M. Lowey, Democrat of New York and the chairwoman of the House Appropriations Committee, said in an interview this month. “We have to see what the Senate actually delivers.”
There is some optimism that a portion of the government could be funded before the deadline.
“I’m confident we can make significant progress on regular appropriations this month,” said Senator Mitch McConnell, Republican of Kentucky and the majority leader, in his first floor remarks after the summer recess. “We have the parameters in place,” he added. “Now it is time for the rubber to meet the road.”
Lawmakers in both chambers say they expect Congress to approve a short-term spending bill to extend the deadline into late November or December. But cementing even that brief reprieve could be arduous: The administration has already asked for any such measure to include money for additional border barrier construction, and Democrats have said they would flatly refuse.
That leaves a deep sense of uncertainty on Capitol Hill about the prospect of resolving dozens of thorny spending issues that also have major political implications. Mr. Trump himself is yet another wild card, given his track record of upending bipartisan funding agreements at the last moment.
“The worst of all worlds, however, would be a government shutdown,” said Senator Susan Collins, Republican of Maine and a member of the Senate Appropriations Committee. “I don’t know of anyone who thinks that is a good idea.”
Lawmakers on the two Appropriations Committees, with reputations as some of the most bipartisan voices on Capitol Hill, have long agreed that left to their own devices, they could easily seal a deal well before the Oct. 1 deadline. But the extended window also widens the possibility that external factors — the administration’s efforts to build the wall along the southwestern border, or the fiscal hawks in Mr. Trump’s inner circle — could further complicate negotiations.
The fevered push to produce a legislative response to the deadly shootings in Texas and Ohio, for example, will most likely intensify pressure from House Democrats to ensure that government funding for gun violence research remains in the final legislation. And while the Pentagon’s redirection of military construction funds to pay for the border wall prompted a bipartisan outcry, there is little agreement over whether Congress should replace money it has explicitly denied Mr. Trump.
“We will strongly oppose any request by this administration to provide additional money for the projects it has decided to defund,” Senators Patrick J. Leahy of Vermont, Brian Schatz of Hawaii and Richard J. Durbin of Illinois, all Democrats on the Appropriations Committee, said this month in a statement. “The funds already appropriated should be used as Congress intended.”
Lawmakers will also have to confront the same debates that allowed the nation’s longest government shutdown to drag into the first few weeks of the 116th Congress: how much money to allocate to Mr. Trump’s border wall, and how much money to devote to agencies tasked with carrying out the administration’s hard-line immigration policies.
House Democrats, in particular, are eager to use the spending process to protest and rein in the administration’s immigration agenda, especially after efforts to append tougher humanitarian standards to a $4.6 billion supplemental bill failed this year. Reports of continuing squalor and overcrowding inside immigrant detention facilities and the refusal by the Republican-controlled Senate to take up a House-passed immigration overhaul have intensified pressure on Democratic leaders to cut off funding for immigration agencies.
Liberal activists have long called for withholding funds from Immigration and Customs Enforcement, the agency that carries out deportations, and Customs and Border Protection. But those efforts are all but certain to fall flat in the Senate and are unacceptable to Mr. Trump.
They are also likely to reignite divisions inside Democratic ranks, where progressives eager to undercut Mr. Trump’s immigration agenda are at odds with centrists in Republican-leaning districts who are reluctant to embrace any reduction in funding for law enforcement.
“You have to be a realist,” said Senator Shelley Moore Capito, Republican of West Virginia, who oversees the appropriations subcommittee responsible for funding the Department of Homeland Security.
“I can understand some of their frustrations, too, because of the acrimony over those three things: the wall, the Border Patrol and ICE,” Ms. Capito said in a phone call after returning from a tour of the southwestern border. “I don’t agree with them, but I see them.”
Congressional leaders agreed this year to remove any provisions deemed so-called poison pills — hot-button policy items that would prompt a partisan fight — as part of the budget agreement that set funding levels for the year and postponed the threat of the government capitulating on the nation’s debt.
Yet it is unclear how broadly each side chooses to define “poison pill,” which could complicate any negotiation.
“Do people want a deal or do they want a fight?” said Representative Tom Cole, Republican of Oklahoma and a member of the House Appropriations Committee. “There’s going to be plenty of yelling and screaming on our side of the aisle, too.”