Washington  - US President Barack Obama met with top military leaders at the Pentagon on Wednesday to receive assessments on the conflicts in Afghanistan and Iraq.

Obama met with Defence Secretary Robert Gates and the Joint Chiefs of Staff as he considers options for winding down the military role in Iraq and reinvigorating the fight against al-Qaeda and the Taliban along the Afghan-Pakistani border.

Gates told senators during testimony on Tuesday that he was preparing a range of options for Obama's consideration and the risks associated with each. Obama has said he wants to end the US combat role in Iraq within 16 months after taking office, but has also said he was seeking a "responsible" drawdown of forces.

"We're going to have some difficult decisions that we're going to have to make," Obama said after emerging from the meeting.

The chairman of the Joint Chiefs of Staff, Admiral Michael Mullen, has warned against premature withdrawals and that the security gains made in Iraq during the last two years are reversible.

Former president George W Bush set into motion a plan for force reductions when he reached an agreement with the Iraqi government that calls for the withdrawal of all
143,000 troops by 2011, along with a pullout from Iraqi cities by midsummer this year.

Obama views Afghanistan as the central front in the war on terrorism and has vowed to increase the US presence there by redeploying forces from Iraq. There are about 34,000 US soldiers in Afghanistan. The military wants to double that number.

Gates said two more brigades could arrive in Afghanistan by the end of spring, with a third one sometime in the summer. The security environment has sharply worsened in the last two years as a resurgent Taliban has stepped up attacks by seeking refuge in Pakistan's tribal areas near the border.

"There is little doubt that our greatest military challenge right now is Afghanistan," Gates told the Senate Armed Services Committee. (dpa)