A senior White House official says U.S. President Barack Obama is calling on his national security team to revise the options for the U.S. war strategy in Afghanistan.

Mr. Obama asked for the changes Wednesday during the latest review of his Afghanistan policy.  The official says the president wants his advisors to determine how and when U.S. troops can hand over security responsibility to the Afghan government. 

Administration officials say Mr. Obama wants to make clear to Afghan President Hamid Karzai that the U.S. commitment in Afghanistan is not "open-ended."

The president's call for revisions comes as the U.S. ambassador to Afghanistan, Karl Eikenberry, has expressed serious reservations about sending additional troops to the country.

Officials say Eikenberry sent two classified cables to Washington last week expressing doubts about Mr. Karzai's leadership.  The Afghan president has been blamed for allowing rampant corruption under his watch.

A spokesman for the U.S. Embassy in Kabul refused to comment on the memos.  The spokesman tells VOA that Ambassador Eikenberry anticipates the Afghan people will "come to expect more from their government," including "clean and competent leadership."

Eikenberry served as the commander of U.S. troops in Afghanistan in 2006 and 2007.  He became ambassador to Afghanistan earlier this year after retiring from the military.

His position puts him in stark opposition to General Stanley McChrystal, the commander of U.S. and NATO forces in Afghanistan, who has requested 40,000 more troops -- which would boost the U.S. commitment in Afghanistan to more than 100,000 troops.

The White House has said Mr. Obama is considering four options, including one that would send 10,000 to 15,000 additional troops, and one that would comply with General McChrystal's request.

The president is not expected to announce a final decision until after he returns from a nine-day trip to Asia that begins Thursday.