The Pentagon says combat operations have halted in southern Afghanistan following one of the biggest battles in months between rebel forces and U.S. and Afghan troops.

A Pentagon spokesman said U.S. and Afghan forces have cordoned off an area close to the Pakistan border following a serious clash with armed rebels that left at least 18 rebels dead.

The spokesman said combat operations have now halted but further search-and-destroy patrols will be carried out.

Already, the spokesman said U.S. and Afghan forces have uncovered one weapons cache. The Pentagon said it does not yet have a detailed inventory of the contents.

The activity began Monday when a small group of U.S. Special Forces soldiers working with Afghan militia came under fire several kilometers north of the town of Spin Boldak.

One of the attackers was killed, a second wounded and a third captured. The Pentagon said the detainee revealed a large rebel contingent of some 80 fighters is hiding nearby.

Helicopters were called in and came under fire as they checked the report. More U.S. troops were mobilized and aircraft called in to bomb a series of caves where the rebels were located.

The Pentagon says at least 18 rebels in all were killed in the action, which saw B-1 bombers and F-16 fighter jets drop a total of 21 heavy bombs.

The U.S. military believes the rebel fighters are closely linked to Hezb-e-Islami movement of renegade Afghan leader Gulbuddin Hekmatyar. He is suspected of trying to align his forces with remnants of the al-Qaida terrorist network and Afghanistan's ousted Taleban regime.