A rocket was fired at a building housing US agents hunting al-Qaeda and Taliban fighters in northwestern Pakistan near the Afghan border.
No casualties were reported.
One rocket landed near the vocational training institute in Miranshah town where the Americans are staying but failed to explode. Tribal militia officers told reporters the device was defused and no damage was caused.
They said the tribal militia during a search for the perpetrators of the attack found another rocket in a forest 200 meters away.
The second missile was fitted with a timer, an officer said.
This was the third rocket attack in Miranshah this month.
Last Tuesday a rocket destroyed the boundary wall of the training institute housing the US agents but no one was injured, local officials said.
A similar attack on the same building on May 1st caused minor damage but no casualties.
No group has claimed responsibility for the attacks.
A small number of US "communications experts" are operating in the area in support of Pakistani forces hunting al-Qaeda fighters and leaders of the Taliban militia.
Taliban sympathisers and fundamentalist religious leaders have demanded the US troops withdraw from the area.
President Pervez Musharraf has insisted their role is restricted to helping with communications and intelligence-sharing.
AFP