By ANDREW TAYLOR and ALAN FRAMWASHINGTON (AP) â¿¿ A Capitol Hill deal to avert the "fiscal cliff" was proving elusive Sunday as a deadline to avert tax hikes on virtually every American worker and block sweeping spending cuts set to strike the Pentagon and other federal agencies grew perilously near. Senate Majority Leader Harry Reid, D-Nev., and Senate Republican leader Mitch McConnell remained at odds on such key issues as the income threshold for higher tax rates and how to deal with inheritance taxes, among other issues. McConnell complained that Reid had yet to respond to a GOP offer made Saturday evening and reached out to Vice President Joe Biden, a longtime friend, in hopes of breaking the impasse. Biden assumed the lead role for Democrats, and a McConnell spokesman said the Kentucky Republican and the vice president were expected to negotiate by telephone into the night. Rank-and-file lawmakers left the Capitol Sunday night with hopes that their leaders would give them something to vote on when they returned Monday morning. One sign of progress came as Republicans withdrew a long-discussed proposal to slow future cost-of-living increases for Social Security recipients as part of a compromise to avoid the cliff. Democrats said earlier Sunday that proposal had put a damper on the talks, and Republican senators emerging from a closed-door GOP meeting said it is no longer part of the equation. "I was really gratified to hear that Republicans have taken their demand for Social Security benefit cuts off the table. The truth is they should never have been on the table to begin with," Reid said late Sunday afternoon. "There is still significant distance between the two sides, but negotiations continue." At stake are sweeping tax hikes and across-the-board spending cuts set to take effect at the turn of the year. Taken together, they've been dubbed the fiscal cliff, and economists warn the one-two punch â¿¿ which leaders in both parties have said they want to avoid â¿¿ could send the still-fragile economy back into recession. Tax cuts enacted in 2001 and 2003 expire at midnight Monday, and $109 billion in across-the-board cuts in federal spending this year would also begin this week.