Gates suggested that the unmanned Predator missions may have already begun. He said he believed that the first flights were launched Thursday but were called back due to poor weather.

"The president has said that where we have some unique capabilities, he is willing to use those," Gates said. "And I think that today may in fact have been their first mission."

Gates said the Predator drones offer a "modest contribution" to NATO efforts to support rebels fighting embattled Libyan leader Moammar Gadhafi's forces there, though Gadhafi is not a specific target.

Unmanned aerial vehicles offer more precise targeting, because their low-flying capability allows for better visibility, "particularly on targets now that have started to dig themselves into defensive positions," Gates said.

He said the drones are needed for humanitarian reasons, and they have capabilities that larger aircraft such as A-10s and C-130s cannot provide.

Vice Joint Chiefs Chairman Gen. James Cartwright said the added precision is necessary because forces loyal to Gadhafi "nestle up in crowded areas" to maximize civilian casualties.

"It's very difficult to identify friend from foe," Cartwright said, noting that the drones facilitate identification of individuals on the ground.

Remote Predator operators are now permitted to strike Gadhafi's defense missions, including air defense, missile and radar sites. Predator strikes are also authorized for civilian protection and can hit Gadhafi's troops, military installations and equipment in the field.