President Barack Obama’s top fiscal negotiator pressed Republicans on Sunday to offer specifics on deficit reduction, and predicted they would agree to raise tax rates on the rich to secure a year-end deal to avoid possible economic doom.

Treasury Secretary Timothy Geithner said “I can’t promise” that the United States won’t go over a looming “fiscal cliff,” triggering automatic tax hikes for most Americans and deep spending cuts in early 2013. He insisted it is up to Republicans.

“That’s a decision that lies in the hands of the Republicans that are now opposing an increase in tax rates” for the wealthiest Americans, a key sticking point in negotiations for a broad deficit-reduction deal, Geithner told “Fox News Sunday.”