Pakistan has replaced Iraq as al Qaeda's main focus, a senior US military commander told the Wall Street Journal.

"Iraq is now a rear-guard action on the part of al Qaeda," General James Conway, the head of the Marine Corps and a member of the Joint Chiefs of Staff, told the paper in interview. "They've changed their strategic focus not to Afghanistan but to Pakistan, because Pakistan is the closest place where you have the nexus of terrorism and nuclear weapons."

The paper said senior US military and civilian officials have grown increasingly pessimistic about Afghanistan and Pakistan. More US troops are killed in Afghanistan each month than in Iraq, and Afghan civilian casualties have been soaring, the said.

Many US officials fear that the additional American forces won't be enough to stabilise Afghanistan unless Pakistan takes stronger measures against the militants who operate in havens in its tribal areas.

General Conway said in the interview that Pakistan's best troops were deployed along its border with India and weren't being used in the fight against the country's militants. Pakistan's leadership doesn't yet seem to accept that terrorism poses an existential risk to the country's future, he added. "Pakistan has to understand there's a dire threat there that they have to act against," he said.