WASHINGTON » President Barack Obama vowed Thursday to delay Congress’ year-end vacation as well as his own for "as long as it takes" to extend Social Security payroll tax cuts and long-term jobless benefits, his second challenge in as many days to conservative Republicans.

Obama stated his position as the House GOP leadership put the finishing touches on legislation that meets White House specifications in important areas but also contains at least one provision the president has pledged to veto.

A vote in the House is likely early next week, and party officials said the president’s threatened veto, which relates to a proposed oil pipeline from Canada to Texas, had made it easier to round up support from conservatives.

Separately, the two parties skirmished inconclusively in the Senate — each side blocking action on the other’s payroll tax alternative — in a showdown that dramatized the partisan nature of the struggle nearly a full year in advance of the 2012 elections.

Given the slow economic recovery and the political appeal of renewing tax cuts and unemployment benefits, it seems likely compromise legislation will reach the president’s desk in the next two weeks. And while there were signs of an emerging consensus on key points, the day’s events made it clear both sides had decided there was still time to bicker.