The top Democrat in the House of Representatives has expressed hope that US lawmakers will reach a deal by mid-December to avoid the fiscal cliff but stood firm on tax rises for the rich.
In an interview with ABC television's This Week, Nancy Pelosi said she would not accept an agreement that keeps tax rates for the wealthy unchanged, as the Republicans in Congress are demanding.
President Barack Obama "made it very clear in his campaign that there are not enough resources", Pelosi said in the interview aired on Sunday.
"Just to close loopholes is far too little money.... If it's going to bring in revenue, the president has been very clear that the higher income people have to pay their fair share."
The fiscal cliff is a poison-pill law agreed by Republicans and Democrats in August last year whereby $US600 billion ($A584 billion) worth of automatic budget cuts and expiring tax cuts would come into force on January 1, likely throwing the world's biggest economy back into recession.
After meeting with Obama at the White House following his November 6 re-election, congressional leaders are trying to hammer out a deal on long-term deficit reduction that includes both higher revenues and spending cuts.
House Speaker John Boehner has indicated that his fellow Republicans, who hold a majority in the lower chamber, would accept some revenue increases so long as they are coupled with "significant" spending cuts.
Boehner sits atop a restive coalition of ultra-conservative Republican lawmakers and faces a tough sell in any deal that eventually includes any kind of tax hikes - or "increased revenues" in government parlance.
Pelosi said negotiators in Congress were hard at work to avert the looming fiscal disaster.
"The spirit at the table was one of 'everybody wants to make the best effort to get this done,'" she said.
"Hopefully that is possible; hopefully it is possible by the middle of December so the confidence of the markets, and most importantly the confidence of the consumers, returns to infuse our economy with demand, which creates jobs."