President Donald Trump's Mexican border wall may be delayed as Republicans consider putting its funding on hold.
Senator Roy Blunt said cash for the wall would be left out of a spending bill that must pass by 28 April to avert a partial government shutdown.
His remarks came on Tuesday after Mr Trump requested a supplemental funding bill to include money for the wall along with military programmes.
But Mr Blunt signalled Mr Trump's request could complicate negotiations.
"All of the committees, House and Senate leaderships, are working together to try to finalise the rest of the FY17 bill," said Mr Blunt, a senior member of the Appropriations Committee and his party's leadership.
"My guess is that comes together better without the supplemental."
He added that the supplemental funding could be dealt with "at a later time".
Mr Trump had proposed $1.5bn (£1.2bn) for his wall through Congress as part of the spending bill, which funds federal agencies to the end of the current fiscal year.
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But Democrats have threatened to block the bill if money for the controversial wall is included.
The government would shut down some federal agencies at midnight on 28 April if Congress is unable to pass the spending bill.
A "great, great wall" along the US-Mexican border was a cornerstone of Mr Trump's presidential campaign.
But the plan has faced resistance from both Democrats and Republicans, and has been estimated to cost as much as $21.6bn - more than the price tag the president cited as $12bn.
Republicans are under pressure to keep the government running after they failed to secure a repeal of the Affordable Care Act.
House Speaker Paul Ryan on Tuesday said Republicans would not try to remove federal funding for women's healthcare provider Planned Parenthood in the upcoming bill.
Democrats had also vowed to stop the critical bill if the provision was included.
Mr Ryan added that it would be best accomplished on legislation at a later date.
The president's wall setback comes as the US Department of Homeland Security pushed back a deadline for proposals to build the wall.
The deadline on Wednesday has been changed to 4 April, the department confirmed on Tuesday.
About 20 companies will be selected after the 10-page proposals are submitted on 4 April.
The federal government will then ask a final group of contenders to build prototypes at a meeting in San Diego, California.