Debt ceiling talks between the White House and the Republican opposition appeared at an impasse, with both sides trading accusations as time runs out to avoid a potentially catastrophic US default.

A Republican offer made on late Friday was "a big step back and contained a set of extreme partisan demands that could never pass both Houses of Congress," White House spokesperson Karine Jean-Pierre said in a statement on Saturday.

"It is only a Republican leadership beholden to its MAGA wing — not the President or Democratic leadership — who are threatening to put our nation into default for the first time in our history unless extreme partisan demands are met," she said, referring to the far-right of the Republican Party.

The White House, determined not to let Republicans blame Democrats for the situation in the eyes of the public, even sent a memo to newsrooms detailing the proposals.

Meanwhile, top congressional Republican Kevin McCarthy tweeted on Saturday that the White House was "moving backwards" in the talks.

"Unfortunately, the socialist wing of the Democrat Party appears to be in control --especially with President Biden out of the country," he wrote, referring to Biden's trip to Japan for the G7 summit.

With the Treasury Department warning that the US government could run out of money as early as June 1 — triggering massive economic disruption in the world's biggest economy and likely around the globe — the political battle in Washington has see-sawed without any clear sign of resolution.

Economic standoff

Republicans, who control the House of Representatives, are demanding steep budget cuts as a price for allowing an extension of the government's borrowing authority.

The White House is seeking to whittle down those demands, while arguing that the traditionally uncontroversial annual debt ceiling increase is being weaponised for political gain.

Hopes for a settlement took a blow Friday when Republicans walked out of negotiations, declaring a "pause."

However, the talks had restarted hours later, leading Jean-Pierre to say "we are indeed optimistic."

Biden, who has expressed a willingness to be patient and said he was not worried, leaves Japan for Washington on Sunday, cutting short a trip that had been set to take him to Papua New Guinea and Australia next week.

More borrowing is required by the US government to meet expenditures already made, meaning failure to strike a deal to lift the debt ceiling would leave Washington unable to pay its bills, triggering an array of economic shockwaves.

"We're making 0 demands to avoid default. You're the only ones with a hostage," tweeted White House spokesperson Andrew Bates late on Saturday, accusing Republicans of seeking to trigger a recession.