Millions of Americans braced on Monday for pay and welfare cheques to stop within days as Congress careened toward a damaging government shutdown, with Republican right wingers blocking attempts to pass a budget.

Four months after barely avoiding the more serious prospect of a credit default, the world's largest economy is once again on the verge of a convulsion, with the lights due to go out at the weekend.

Republicans leading the House of Representatives – hamstrung by hardline rebels demanding deep spending cuts – have been unable to pass the usual series of bills setting out departmental budgets for the next financial year, which begins on Sunday.

The party's leadership does not even have the votes to advance a short-term funding bill at 2023 spending levels – known as a continuing resolution – to keep the government open past midnight on Saturday.

A shutdown would put at risk the finances of workers at national parks, museums and other sites operating on federal funding, but it could also carry significant political risk for Biden as he runs for re-election in 2024.

The White House warned on Monday that seven million people who rely on the food aid programme for women and children known as WIC could also see their money stopped.

"During an Extreme Republican Shutdown, women and children who count on WIC would soon start being turned away at grocery store counters, with a federal contingency fund drying up after just a few days and many states left with limited WIC funds to operate the programme," a spokesman said in a statement.

The deadlock arose after House Republicans refused to support the government spending levels agreed between Biden and Speaker Kevin McCarthy, the top Republican in Congress, that would keep government gears turning.

Another major sticking point has been a request for additional aid for Kyiv, after Ukrainian President Volodymyr Zelenskyy visited Congress last week pleading for more weapons to battle Russian forces 18 months into the war.

Both parties in the Senate support the US$24 billion aid bill. But a handful of hardline Republicans in the House are threatening to block any funding measures that include the aid. (AFP)