Washington DC - Lawmakers signaled Sunday they were open to talks to avert a fast-approaching federal government shutdown after the Trump administration raised the stakes by threatening mass federal firings if there is no agreement.

President Donald Trump, a Republican, is in a tense showdown with congressional Democrats on spending plans ahead of a fiscal deadline of midnight on September 30, after which key services will be cut.

He has struck a defiant tone in pushing for his own agenda and last week canceled a meeting to discuss the stalemate with senior opposition leaders, which will instead take place Monday.

Trump is "open to discussion" and "wants to operate in good faith," House Speaker Mike Johnson, the highest-ranking Republican in Congress, said on CNN.

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But he was evasive when asked if Monday's meeting would involve any negotiation, saying: "We'll have to see."

Shutdown battles have become a regular feature of US politics under both Republican and Democratic administrations in an increasingly polarized Washington.

The White House upped the ante last week by ordering government agencies to prepare for layoffs that would go beyond the usual practice of temporary furloughs during government shutdowns.

The move would add to the pain of government workers after large-scale firings masterminded by tycoon Elon Musk's Department of Government Efficiency earlier this year.

Hakeem Jeffries, the Democratic House leader, said on ABC that he was "hopeful" that a deal could be struck before the Tuesday cutoff.

His colleague Chuck Schumer, the Democrats' Senate leader, echoed that guarded optimism and said any potential breakthroughs would depend on Trump's Republicans.

"If the President at this meeting is going to rant and just yell at Democrats and talk about all his alleged grievances and say this, that, and the other thing, we won't get anything done," he said on NBC.

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"But my hope is it will be a serious negotiation."

Congress last faced a shutdown in March, when Republicans refused talks with Democrats over Trump's massive budget cuts and the layoff of thousands of federal employees.

During the last showdown, lawmakers voted to keep the lights on through September with hours to spare, after Senate Minority Leader Chuck Schumer announced he would back the Republican-drafted proposal.