Barack Obama has given the go-ahead for unmanned drone aircraft to operate in the skies above Libya.
Rebels have welcomed the news saying the weapons will help protect civilians.
They have already proved to be potent attackers in Pakistan and Afghanistan, particularly in areas where the US has no troops deployed.
The predators can remain in the sky virtually non-stop, firing missiles unseen, and with no crewmembers at risk.
The US Defense Secretary Robert Gates said: ‘The president has said where we have some unique capabilities he is willing to use those, and in fact he has approved the use of armed predators, and I think today may, in fact, have been their first mission. I think that will give us some precision capability.’
One reason for the drone deployment is the continued siege of Misrata, the rebel-held stronghold in the west of Libya.
The US said Gadaffi’s forces were carrying out ‘vicious attacks’ there.
Rebel fighters had become frustrated with the NATO operation in Misrata saying it was too cautious.
Hundreds of people are believed to have died in the city where food and medical supplies are running out.