The United States is looking at bolstering its military presence in the Gulf after US troops stationed in Iraq withdraw by the end of the year, a US defense official said Monday.

Amid concerns about Iraq's stability and Iran's role in the region, the Pentagon was weighing a move to shift some of the 39,000 forces due to leave Iraq to neighboring Kuwait, the official, who spoke on condition of anonymity, told AFP.

A Pentagon spokesman said he was not aware of any negotiations with Kuwait on stationing more US troops there.

"I think we're going through a range of options right now about what it could look like, what it should look like going forward and no decisions have been made," Pentagon spokesman Captain John Kirby told reporters.

The New York Times first reported the possible plan over the weekend, and said commanders -- mindful of Iran's influence -- also were considering stepping up the presence of US warships in the Gulf region.

Kirby said the ultimate arrangement of US forces in the Gulf would be drawn up in line with security agreements with US allies.

"Whatever decisions are made about force posture, it's going to be based on our security commitments that we have made and continue to honor in that region, not aimed at any particular threat," he said.

President Barack Obama announced this month that the remaining US troops in Iraq would leave by the end of the year, after negotiations with Baghdad on a possible post-2011 force collapsed over the question of legal immunity for American soldiers.

Defense Secretary Leon Panetta, speaking during a visit to Asia last week, warned Tehran against misinterpreting the withdrawal of US troops from Iraq and cited the vast network of US bases in the region.

"For Iran and anybody else who has any other ideas, let me make clear that the United States maintains 40,000 troops in that region, 23,000 in Kuwait, and numbers of others in countries throughout that region," Panetta said.

Iranian Foreign Minister Ali Akbar Salehi dismissed Washington's warnings and said Monday during a visit to Baghdad that the United States is not following a "rational" approach in its reported plan to boost military forces in the Gulf.