U.S. defense officials have detected hundreds of suspected al-Qaida and Taleban fighters grouping in eastern Afghanistan. But so far U.S. forces have taken no action against them.

Call it a glimpse into the shadow war in Afghanistan.

Air Force Brigadier General John Rosa of the Pentagon's Joint Staff began Friday's military briefing at the Pentagon with a short, routine statement. "The situation in Afghanistan remains the same," he said. "We remain focused on locating and destroying the elements of al-Qaida and Taleban."

He gave no details. But later, under questioning, General Rosa disclosed U.S. forces have spotted hundreds of possible al-Qaida and Taleban fighters grouping in the Gardez area of eastern Afghanistan. "I wouldn't say specifically al-Qaida, but there's hundred of folks, and we don't know the makeup," he said. "But they're certainly not friendly."

Under further questioning, General Rosa admitted U.S. forces have not attacked the group to kill or capture the hostiles. "We've observed, we've gathered intelligence," he said. "But to this date, we haven't acted."

Military officials, speaking on condition of anonymity, offered several explanations for the lack of immediate military action against the group. They said U.S. commanders may be waiting to see if more fighters join the gathering or whether fugitive senior Taleban or al-Qaida leaders show up.

But these officials also conceded U.S. troops may be holding back out of concern the apparently hostile forces might be civilians unconnected to al-Qaida or the Taleban.

The Pentagon has in recent weeks come under criticism in the wake of news reports about botched raids that claimed civilian lives, including the lives of supporters of the new U.S.-backed interim government.