US President Barack Obama has demanded an end to a three-day government shutdown he decried as a reckless "farce", piling pressure on Republicans to climb down first on a budget impasse.
The US Treasury meanwhile warned of "catastrophic" consequences if there's no deal within weeks to raise the country's debt ceiling, and the IMF chief said navigating a way out of that next crisis was "mission critical".
Obama travelled to the Washington suburbs to lambast Republican House Speaker John Boehner, who emerged from a White House meeting late on Wednesday complaining the president would not negotiate with him.
"Take a vote, stop this farce and end this shutdown right now," Obama said during a fiery speech in the Maryland suburb of Rockville, home to many federal workers laid off in the shutdown.
Branding the crisis a "reckless Republican shutdown", Obama said Boehner could reopen the government and get hundreds of thousands of people back to work "in just five minutes" by passing a temporary operating budget with no partisan strings attached.
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"Speaker John Boehner won't even let the bill get a yes or no vote, because he doesn't want to anger the extremists in his party," Obama said.
The government ran out of money on Monday, after Congress failed to pass a budget, forcing authorities to send all non-essential workers home and to close museums, monuments and national parks that are all popular with tourists.
The Democratic-led Senate had turned back repeated Republican efforts to pass a budget while defunding or delaying Obama's health care law, which is a centrepiece of his political legacy and reviled by Tea Party conservatives.
The talks at the White House between Obama and congressional leaders made no progress, and there is no sign the dispute will be solved before dragging into a second week.
The crisis rattled Wall Street on Thursday, where the Dow Jones Industrial Average dropped 136.66 points (0.90 per cent) to 14,996.48, amid ongoing jitters from the shutdown and nervousness about a looming battle over Congress's responsibility to raise the $US16.7 trillion ($A17.8 trillion) US statutory borrowing limit.
If there's no resolution before October 17, the government could begin running out of money to pay its bills and an unprecedented US debt default could result.
But Republicans are again demanding concessions on Obamacare before voting to raise the debt ceiling, raising fears of unpredictable consequences, which the Treasury said in a report Thursday could plunge the US into deep recession and rock global markets.
Obama has refused to negotiate with Republicans over raising the debt ceiling, saying Congress is simply authorising borrowing to pay bills it has already run up and that offering concessions would set a poor precedent for future presidents.
