Republicans say it's Democrats who are dragging out the talks.
"In the past 48 hours, the president has not been negotiating in good faith in my opinion," said Rep. Pat Tiberi, R-Ohio, who said he was increasingly pessimistic that a deal could be reached.
"I believe we can get to a point on revenues that we can get something done, but the problem is the White House and the president refuse to get serious about spending," House Majority Leader Eric Cantor, R-Va., said.
While Republicans are flummoxed on taxes, liberal Democrats are trying to pull Obama in the opposite direction on Medicare and Social Security. Eighteen months ago, Obama had all but agreed to an increase in the Medicare retirement age and a less generous inflation adjustment for calculating Social Security COLAs.
Now, House Minority Leader Nancy Pelosi is warning against raising the Medicare eligibility age, saying such a move wouldn't contribute much savings toward an agreement in the short term.
Democrats are also pushing back against a GOP plan to reduce Social Security cost-of-living adjustments, another step back from where Obama and Boehner were just 18 months ago.
"Quite frankly, Social Security is off the table," Rep. Joe Crowley, D-N.Y., said.
The backtracking has Republicans fuming that Obama campaigned on a "balanced" fiscal solution but now is unwilling to pair tax increases with politically painful cuts to Medicare and other popular programs.
Associated Press writers Alan Fram and Nyia Hawkins contributed to this report.