In a blow to president Barack Obama, the US Senate effectively killed a jobs bill at the heart of his efforts to turn the US economy around in the run-up to the November 2012 elections.

Politicians voted 50-49 to advance the $US447 billion ($452 billion) plan, falling short of the 60 senators needed to do so, in the face of fierce opposition from Republicans eager to deny the president a second term.

"Tonight's vote is by no means the end of this fight," Mr Obama said in a statement released before the vote was complete.

He vowed to move his plan through piecemeal "as soon as possible".

He also promised to pile political pressure on Republicans in a series of votes aimed at forcing them to oppose funds aimed at helping middle class families and block tax hikes on the very richest Americans to pay for the plan.

"With so many Americans out of work and so many families struggling, we can't take 'no' for an answer. Ultimately, the American people won't take 'no' for an answer," the embattled president said.

The bare majority vote inflated Senate support for the measure, as some Democrats who backed ending debate on the legislation had said they would oppose its final passage - a point that led Republicans to crow that a bipartisan majority was rejecting the bill.

Mr Obama has spent weeks demanding Congress pass a full version of a bill designed to boost growth, cut the unemployment rate of 9.1 per cent and shield the fragile US recovery from the threat of European debt contagion.

AFP