S&P 500 futures fell at the open of electronic trading as investors grew increasingly worried at the lack of progress. The benchmark S&P was down 1 percent, or 14 points, to 1326.00.
Early currency trading suggested a move away from the dollar, with the biggest drop in the greenback coming against the Swiss franc. In early Asian trading, the dollar dropped to 0.8121 against the Swiss franc, down 0.7 percent.
The decline in futures points to a poor open for U.S. markets.
White House officials and Republican leaders scrambled on Sunday to reassure global markets the United States would avert a debt default, but the two sides were still not close to a deal. House Speaker John Boehner told fellow Republicans on a conference call that a large-scale debt deal was not possible with President Barack Obama.
An aide to Senate Majority Leader Harry Reid told Reuters on Sunday the Nevada senator was outlining a plan that would cut $2.5 trillion in spending and increase the debt limit that he hoped would be brought to the Senate floor this week.
Earlier in the day, White House Chief of Staff Bill Daley warned that there would be a "few stressful days" ahead for financial markets.
"There's an old saying that things don't matter until the day they matter; we're getting close to the day when it will matter," said Quincy Krosby, market strategist at Prudential Financial in Newark, New Jersey.
In the past few days, markets see-sawed on reports suggesting progress toward an agreement to cut the deficit that would allow for the U.S. debt ceiling to be raised and avert a default that is likely to roil markets.