Prospects for extending President Barack Obama's signature payroll tax cut, once considered a slam dunk on Capitol Hill, now seem far less certain as House-Senate talks have deadlocked over finding ways to pay for it.

In a contentious negotiating session Tuesday, Democrats came out against House GOP proposals to pay for the 2 percentage point payroll tax holiday by freezing federal workers' pay and requiring more affluent seniors to pay more for Medicare premiums.

After four public sessions, the House-Senate talks have failed to yield a single significant breakthrough. Michigan Rep. Dave Camp, the top GOP negotiator, has turned the focus to finding ways to foot the bill for $150 billion to $160 billion cost of the payroll tax cut, renewed jobless benefits and other measures through year's end.

(Copyright 2012 by The Associated Press. All Rights Reserved.)