The White House says there are still serious differences with Republican negotiators in debt ceiling talks as the two sides seek to reach a deal.

White House spokesperson Karine Jean-Pierre told reporters in Japan, where US President Biden is attending a meeting of Group of Seven leaders, that negotiators would continue to work toward a reasonable solution to avoid default.

"We are still optimistic," she said.

She also questioned whether congressional Republicans were serious about wanting to cut the deficit and reaching a "reasonable" deal.

Biden's administration is reaching for a deal with Republicans, led by House of Representatives Speaker Kevin McCarthy, as the US faces a deadline as soon as June 1 to raise the country's borrowing borrowing limit, now at $US31 trillion, to avoid a default that would send shockwaves through the global economy.

Top Republican negotiators for McCarthy said after the Friday evening session that they were uncertain on next steps. But the White House publicly expressed optimism that a resolution could be reached if parties negotiated in "good faith."

"We re-engaged, had a very, very candid discussion, talking about where we are, talking about where things need to be, what's reasonably acceptable," said Republican Garret Graves, a top McCarthy ally leading the talks.

Another Republican negotiator, Patrick McHenry of North Carolina was asked if he was confident an agreement over budget issues could be reached with the White House, McHenry said: "No."

Counsellor to the president Steve Ricchetti, who is leading talks for the Democrats, said he was hopeful.

"We're going to keep working," he said.

Republicans want to extract steep spending cuts, arguing the nation's deficit spending needs to get under control, rolling back spending to fiscal 2022 levels and restricting future growth.

However Biden's team said the caps Republicans proposed in their House-passed bill would amount to 30 per cent reductions in some programs if defence and veterans are spared, according to a memo from the Office of Management and Budget.

US Treasury Secretary Janet Yellen warned that if the deadlock is not broken, the Biden administration faces a catastrophic default.

with AP