The U.S. agreed to NATO's request for a 48-hour extension of American participation in coalition airstrikes against targets in Libya and U.S. lawmakers cautioned Sunday the allies need to know more about the rebels fighting Moammar Gadhafi's forces before providing them with weapons.

Two weeks into the assault on Gadhafi, Republican lawmakers expressed concern that a stalemate could leave him in control of portions of Libya and with access to stockpiles of chemical weapons.

The U.S. is shifting the combat role to Britain, France and other NATO allies, but American air power is still in demand. Air Force AC-130 gunships and A-10 Thunderbolts and Marine Corps AV-8B Harriers will continue to attack Gadhafi's troops and other sites through Monday evening. These aircraft are among the most precise in the American arsenal.

After Saturday, no U.S. combat aircraft were to fly strike missions over Libya unless NATO officials specifically asked and authorities in Washington gave their approval. NATO assumed full control last week from the U.S.-led international force for all aspects of the operation in Libya as authorized by U.N. resolutions that include an arms embargo, enforcing the no-fly zone, and protecting civilians from Gadhafi's forces.

In an emailed statement, NATO spokeswoman Oana Lungescu said Sunday that "poor weather conditions over the last few days" were the reason the alliance made the request. She would not elaborate. "This is a short-term extension which expires on Monday," she said.

A senior U.S. military official said heavy cloud cover over Libya late last week curtailed allied airstrikes. Gadhafi took advantage of the lull, pushing east into the port cities of Ras Lanouf and Brega, the official said on condition of anonymity to discuss sensitive military planning. The 48-hour extension is intended to roll back the progress made by Gadhafi's army, the official said.