Washington  - Withdrawing US forces from Afghanistan is not among the options under consideration by US President Barack Obama as he outlines a new strategy for the conflict.

"I don't think we have the option to leave," White House spokesman Robert Gibbs said Monday. "I think that's quite clear."

Obama is in the middle of a strategic review and assessing various possibilities for the war in Afghanistan that is entering its ninth year. The top US commander there, General Stanley McChrystal, is reportedly seeking an additional 40,000 troops.

There are already more than 60,000 American soldiers on the ground, and Obama is facing resistance from within his own Democratic Party in Congress over deploying more forces.

McChrystal last week warned of failure in Afghanistan unless more troops are sent, prompting national security adviser James Jones to say on television over the weekend that it would be better if military leaders kept their conclusion within the chain of command.

Obama will meet with congressional leaders on Tuesday to discuss the process and will hold another meeting later this week with his top advisors. The White House has said it will be weeks before any final decisions are made.  dpa