Sunday was "a critical day" in the political showdown in Washington as Republicans and Democrats struggle to get a deal to raise the nation’s debt limit, a top White House aide said.

White House senior advisor David Plouffe

Sunday was "a critical day" in the political showdown in Washington as Republicans and Democrats struggle to get a deal to raise the nation's debt limit, a top White House aide said.

"We have to get this solved. Today is obviously a critical day. We have to give confidence that there is a pathway" forward, White House senior advisor David Plouffe told NBC television.

He stressed there was no deal yet as Republicans and Democrats go down the wire to reach a deal to raise the $14.3 trillion debt ceiling ahead of a Tuesday midnight (04:00 GMT Wednesday) deadlines.

"We don't have a deal. The hours are ticking," Plouffe said on NBC's "Meet the Press."

"In the coming hours I think it is incumbent on congressional leaders to compromise that one little bit," he said.

He said the deal now being hammered out between the White House, and leading Senate Democrats and Republicans would see an immediate raise of the debt ceiling accompanied by about $1 trillion in spending cuts.

A special committee would then be set up which would be tasked with identifying even more spending cuts by the end of the year.

If it failed to come up with extra cuts, then there would be some kind of enforcement mechanism. "You want something to compel this committee to act," Plouffe said.

The US Treasury has said it would run out of cash on Tuesday to meet the nation's bills which could force the world's economic superpower into default for the first time, threatening the global economy.