The US is concerned insurgents freely cross the Afghan-Pakistan border
Al-Qaeda may be considering shifting its focus from Iraq to Afghanistan, the top US commander in Iraq has said.
In an interview with the Associated Press, Gen David Petraeus said there was evidence that foreign fighters were being diverted away from Iraq.
But he said there was no suggestion the militant Islamist group would entirely abandon the fight in Iraq.
Al-Qaeda evolved in Afghanistan and was closely-linked to the Taleban regime, toppled by US-led forces in 2001.
As Iraq became the main theatre of conflict in the Middle East, al-Qaeda's leadership focused its efforts on fighting there.
"We do think that there is some assessment ongoing as to the continued viability of al-Qaeda's fight in Iraq," Gen Petraeus said.
But he warned: "They're not going to abandon Iraq. They're not going to write it off. None of that.
"What they certainly may do is start to provide some of those resources that would have come to Iraq to Pakistan, possibly Afghanistan."
He said there were signs that foreign fighters recruited by al-Qaeda to do battle in Iraq were being diverted to the largely ungoverned areas on the Afghan-Pakistan border.
The US has often expressed concern at the flow of insurgents through the porous border with Pakistan.
Secretary of Defense Robert Gates recently said he was "working very hard" to find a way to counter the movement of militants through the border.