WASHINGTON >> President Donald Trump and congressional leaders have scheduled a summit to begin sorting out their budget differences, top lawmakers and the White House said today, as a clash that could produce a partial government shutdown by the weekend hung in the balance.

The summit, set for Thursday at the White House, comes just a day before federal spending expires that’s needed to keep agencies functioning beyond midnight Friday night. Complicating the search for a pact are disputes over immigration, health and other issues folded into the year-end mix.

Republican leaders want to push a bill through Congress this week keeping government afloat through Dec. 22 as bargainers seek a longer-term spending pact. But the GOP will need Democratic votes to succeed, and potential opposition from Democrats and GOP conservatives has left the pathway unclear for averting a closure just weeks before the start of the 2018 election year.

Adding an obstacle, the roughly 30 members of the hard-right House Freedom Caucus planned a meeting tonight to discuss the budget clash as their leader said he was against a short-term deal.

Hours before Trump and Capitol Hill leaders were to hold a budget meeting last Tuesday, House Minority Leader Nancy Pelosi, D-Calif., and Senate Minority Leader Chuck Schumer, D-N.Y., abruptly called off the session. The cancellation came after Trump took to Twitter to vilify their stances on taxes, immigration and crime and say he saw no prospects for an agreement, and the standoff has exacerbated bitter feelings on both sides.

“We hope the president will go into this meeting with an open mind, rather than deciding that an agreement can’t be reached beforehand,” they said Monday in a written statement.

The two Democrats pointedly said they’d accepted Trump’s offer to meet with them. And in what seemed an attempt to isolate the president, they said they hoped he’d be amendable to an agreement “as negotiations with our Republican counterparts continue.”

With the budget chafing under spending caps imposed by a 2011 bipartisan budget deal, Democrats want defense and domestic programs to get equal funding increases. Both sides say they want to provide money for a health insurance program that serves more than 8 million children and for states battered by recent storms.

Democrats and some Republicans are also demanding a plan to protect immigrants who arrived illegally in the U.S. as children.

Trump scuttled a program from President Barack Obama’s administration that protected them from deportation, and he gave Congress until March to work out a new agreement. Trump expressed a desire to work with Democrats to extend that program, called Deferred Action for Childhood Arrivals, but he and Republicans want border protection money in return and there have been no signs of progress.

Getting an immigration deal enacted in December would cause an eruption in House GOP ranks, where many conservatives oppose the idea.

In addition, some from both parties want to restore billions in federal payments to health insurers that Trump halted last autumn. There are also demands for money for battling opioid abuse.

White House spokesman Raj Shah and a spokesman for Senate Majority Leader Mitch McConnell, R-Ky., confirmed Thursday’s meeting. But no sooner was it announced than House Freedom Caucus chairman Rep. Mark Meadows, R-N.C., said he opposes a two-week agreement.

“Failing to see what it will accomplish that couldn’t be accomplished in the last 8 weeks,” he wrote in a text message.

He said his group will also discuss the Republican tax bill, the party’s chief legislative priority, at its Monday gathering. The Senate approved its near $1.5 trillion tax legislation before dawn Saturday while the House passed a similar measure in November.

GOP leaders hope to send Trump a final package before Christmas, and there’s a growing consensus that they have a strong chance to succeed. Both chambers’ bills give the bulk of their tax breaks to businesses and wealthier people and are headlined with a cut of the 35 percent corporate tax to 20 percent. They have modest differences over items like whether to reduce or fully repeal the tax on the most expensive estates.

GOP leaders hope that temporarily financing government through Dec. 22 would buy time for a larger agreement. It seems likely that a second temporary bill stretching into January would also be needed for a final pact addressing spending, hurricane aid and perhaps immigration.

For Republicans, such an agreement would unlock a huge budget increase for the Pentagon — perhaps $70 billion for the 2018 fiscal year alone. Democrats would likely win less for nondefense agencies.