Business secretary Vince Cable has hit out at what he described as "a few right-wing nutters" holding up a deal to cut US government debt.
Speaking on the BBC's Andrew Marr Show, Cable called them "a few right-wing nutters in the American Congress".
Unless a deal on Capitol Hill is agreed before 2 August, the US Treasury could run out of money to pay its bills.
A provisional deadline of the opening of Asian markets this morning was missed as US lawmakers failed to reach agreement.
In early trading on Monday, Asian stocks fell more than 82 points, or 0.81%, to 10,050.
Cable said the crisis represented a bigger risk to global markets than the continuing debt woes in the eurozone.
US President Barack Obama wants to cut the US's $1.5trn (£919bn) annual government deficit by both reducing government spending and raising taxes.
A number of Republicans in Congress are opposed to the plans and are holding out for stronger spending cuts in lieu of tax rises.
The two sides have to come to an agreement before the current $14.3tn (£8.7tn) limit on US borrowing can be raised.
An emergency meeting between Obama and congressional leaders on Saturday failed to make a breakthrough.
However, US Treasury Secretary Timothy Geithner said on Sunday that he still expected a deal to be reached.
Geithner told CNN: "It is unthinkable that this country will not meet its obligations on time. It is not going to happen."
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