"Something has gone terribly wrong when the biggest threat to the American economy is the American Congress," said Democratic Senator Joe Manchin of West Virginia.

Americans could see a bigger bite taken out of their paychecks starting on Tuesday as payroll and income tax cuts expire, while 2 million unemployed Americans could see their jobless benefits run out. Government contractors might be forced to lay off employees as $109 billion in automatic spending cuts kick in, and businesses could lose tax breaks for everything from wind power to research and development.

The uncertainty has weighed on financial markets and forced businesses to slow hiring and investment. Market participants braced for more turbulence on Monday.