The Predators, highly successful in operations on the Af-Pak border, carried out a number of strikes in Misrata as well as on suspected missile sites in capital Tripoli giving tactical advantage to the rebels, who drove out dozens of snipers, tall buildings in hours of street fighting, NATO officials said.
With the deployment of armed drones, Washington's involvement in the stalemated conflict appears to deepen and has once again put American assets into a leading strike role against Gaddafi's loyalist ground forces.
The announcement of deployment of armed drones over Libya was made by Defence Secretary Robert Gates, who said this would give allied forces "precision capability" in military operation.
US officials said at least two predators would remain in the Libyan airspace at all times and the Hellfire missile equipped UAVs would prove more effective than A-10 ground attack aircraft.
The unmanned aircraft can hover over an area for upwards of 12 hours at a stretch making them much better at distinguishing rebel troops from loyalist forces than faster moving fighter jets, which also must stay at higher altitude.
Predators carry relatively small Hellfire missiles that are much more effective than precision guided bombs at striking enemy troops in heavily populated areas.
Pan-Arab channel Al Jazeera reporting from the battle scarred Misrata said in recent weeks the sustained NATO air strikes have forced loyalist troops to seek the protection of cities, to make it more difficult to strike at them without causing civilian casualties.