WASHINGTON (Reuters) -A Republican push to advance U.S. President Donald Trump's sweeping tax bill through Congress appeared to hit a roadblock on Thursday, as hardline conservatives demanded deeper cuts to Medicaid in exchange for their support in a key procedural vote.

House Budget Committee Chairman Jodey Arrington warned that the vote, planned for Friday, could be delayed due to opposition to the measure, which could add trillions to the nation's $36.2 trillion in debt over the next decade.

"There are concerns about having to get more information, which would potentially delay this to next week," Arrington, of Texas, told reporters.

He later issued a statement saying he was confident that Republicans on his committee would advance the legislation, even though at least four hardliners had threatened to block it. There was no indication late on Thursday that their positions had changed.

Four "no" votes would be enough to stop the measure from advancing, given Republicans' 21-16 majority on the committee. 

House of Representatives Speaker Mike Johnson insisted that the legislation was still on track for a floor vote next week, while other Republican leaders said disagreements between warring party factions had dwindled to a handful of issues. 

"This is always what happens when you have a big bill like this. There's always final details to work out, all the way up until the last minute, so we're going to keep working," House Majority Leader Steve Scalise told reporters.

The legislation would extend tax cuts passed during Trump's first term. Congress' bipartisan Joint Tax Committee estimates the tax cuts would cost $3.72 trillion over a decade. Trump has highlighted measures including lifting taxes on tips and overtime that Republicans say would boost working-class Americans, while critics say the bill will offer more benefits to the wealthy.

The Republican caucus appeared to be divided between three factions: party moderates from Democratic-led states who want to increase a federal deduction for state and local taxes; hardliners demanding that a bigger SALT deduction be paid for with deeper cuts to the Medicaid health insurance program for low-income Americans; and other moderates determined to minimize Medicaid cuts.    

The budget committee would have to approve the bill for it to reach the House floor.

Two hardline committee members, Representatives Ralph Norman and Andrew Clyde, said they would not support the current legislation. Representative Chip Roy also signaled disapproval while a fourth, Representative Josh Brecheen, called for more time to examine the cost. 

"We've still got a spending problem. We've got a deficit problem. And it doesn't address that," said Norman, a South Carolina Republican. 

Clyde, of Georgia, said in a statement: "I'm a NO on advancing the budget reconciliation bill out of the Budget Committee in its current form. There are numerous issues that we must address."

Republicans hold majorities in both the House and Senate and so far have not rejected any of Trump's legislative requests. Trump is due to be back in Washington next week after his Middle East trip.