WASHINGTON, USA - President Barack Obama's job approval rating has dropped below 50 per cent in a second major poll in an indication he is suffering from the long healthcare debate and weakness in the economy, Gallup said on Friday.

Gallup said 49 per cent of Americans approved of Obama's job performance. A survey by Quinnipiac University on Wednesday had a similar finding, putting him at 48 per cent support.

It was the first time he had fallen below majority support in those two polls. He had been polling in the low 50s for months after taking office in January with an approval rating just under 70 per cent.

Gallup said Obama's drop in its daily tracking poll likely resulted from the contentious debate over healthcare as well as the poor state of the U.S. economy, with millions of Americans out of work.

"Americans are also concerned about the Obama administration's reliance on government spending to solve the nation's problems and the growing federal budget deficit," Gallup said in an analysis of its poll, which surveyed 1,533 people from Tuesday to Thursday. The margin of error was 4 points.

Democrat Obama became the fourth-fastest U.S. president since World War Two to drop below majority support in the Gallup poll, following Republican Gerald Ford, Democrat Bill Clinton and Republican Ronald Reagan.

Peter Brown, assistant director of the Quinnipiac University Polling Institute, said that although Obama's job approval was below 50 per cent for the first time nationally, it was not statistically different from his 50 per cent approval rating in October.

"Nevertheless, in politics symbols matter and this is not a good symbol for the White House," said Brown. "Moreover, the per centage who approve of the way he is handling the economy has dropped from a split 47-46 per cent approval in October to 52-43 per cent disapproval today."