WASHINGTON (Reuters) - The U.S. Congress, back from vacation on Tuesday, already had its plate full with urgent fiscal and disaster relief issues when President Donald Trump saddled it with deciding the fate of people brought illegally to the United States as children.

FILE PHOTO: The U.S. Capitol Building is seen at sunset in Washington, U.S. May 17, 2017. REUTERS/Zach Gibson

The future of almost 800,000 young “Dreamers,” protected from deportation by the Obama-era Deferred Action for Childhood Arrivals (DACA) program, now rests with lawmakers who have failed repeatedly to deal effectively with immigration issues.

Trump on Tuesday scrapped DACA while giving Congress six months to do something about it.

Republican Senator Jeff Flake of Arizona said permanent legislation to fix the immigration system had been Congress’ prerogative all along, and that lawmakers should and could act quickly.

“There’s a program, kids are protected by it, they are going to lose that protection if we don’t act,” Flake said.

Other critical issues are bearing down on lawmakers. Leading U.S. lawmakers said on Tuesday they were preparing to swiftly approve disaster relief for victims of Hurricane Harvey and two other must-pass priorities: preventing a default on U.S. government debt and avoiding a government shutdown.

The House of Representatives was scheduled to consider on Wednesday a first installment of aid for Harvey relief and recovery, about $8 billion, and the Senate’s leadership promised swift action once the House has passed the measure.

Senators will then move on to making sure government creditors are paid and avoiding a government shutdown, Senate Majority Leader Mitch McConnell told the chamber, outlining the agenda for September. “We have to get all three of these things done and we have to do it very quickly.”

‘HOLDING THE LINE’

Republican conservatives were concerned that the various urgent items would be packaged together and rushed through in a way that would prevent lawmakers from attaching conditions that could restrain or even reform government spending.

Representative Mark Walker, leader of a large group of House conservatives, said in an interview with Fox News: “For Republicans, we have to be willing to hold the line when it comes to the out-of-control spending.”

The Senate’s No. 2 Republican, John Cornyn, said Republican leaders were preparing to attach a measure raising the U.S. debt ceiling - unpopular with conservatives - to the Harvey aid package when it arrives in the Senate, The Hill reported. Such a combined measure would then have to be sent back to the House for approval.

“It’s imperative that we get that (Harvey aid) supplemental passed. And the leader has made the decision to attach the debt limit to that, and I support that,” Cornyn told a group of reporters, according to The Hill. The Trump administration has urged that the two measures be combined.

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The debt ceiling caps how much money the U.S. government can borrow, and many conservatives in Congress are loath to raise it without spending reforms.

Representative Mark Meadows, chairman of the conservative House Freedom Caucus, acknowledged on Tuesday evening that conservatives probably did not have the votes to stop a measure combining Harvey aid with a debt ceiling hike.

“It will probably pass, with a majority of Democrats and enough Republicans to get it across the finish line,” Meadows said after a meeting of the caucus. Nonetheless, he said the caucus would propose that a requirement capping government spending as a percentage of gross domestic product be attached to the debt ceiling hike.

Congress must raise the debt ceiling by early October to stave off an unprecedented U.S. government debt default, which would shake global markets. Lawmakers also need to approve by late September a government funding bill or the government will have to close on Oct. 1.