President Barack Obama is raising the threat of a veto if Republicans try attaching controversial oil pipeline or other language to a bill renewing payroll tax cuts and unemployment coverage.

His comments Wednesday intensify their year-end partisan showdown.

Obama's warning -- which prompted an immediate and strong response from the GOP -- signaled that there is no easy end in sight as the two sides maneuver over renewing tax reductions and jobless benefits that without congressional action expire Jan. 1 -- just as the 2012 election year begins.

Top House Republicans are working to overcome conservative resistance to GOP legislation extending this year's 2 percentage point reduction in the 6.2 percent Social Security payroll tax for another year.

(Copyright 2011 by The Associated Press.  All Rights Reserved.)