Armed US Predator¹ drones are to carry out missions over Libya, Defence Secretary Robert Gates has said.

美国国防部长罗伯特·盖茨称，“掠夺者”号武装侦察机将要在利比亚领空执行任务。

Mr Gates said their use had been authorised by President Barack Obama and would give "precision capability²" to the military operation.

Unmanned US drones are already used to target militants³ along the Pakistan-Afghanistan border.

Libyan rebels have been battling Col Gaddafi's troops since February but have recently made little headway（前进，进步） .

"President Obama has said that where we have some unique capabilities⁴, he is willing to use those," Mr Gates told a news conference.

He said two Predators⁵ were being made available to Nato as needed, and marked a "modest contribution" to the military operations.

Mr Gates denied that the drone deployment⁶ was evidence of "mission creep" in Libya and said there were still no plans to put US "boots on the ground" in Libya.

"There's no wiggle room（余地） in that," he said.

Gen James Cartwright, vice-chairman of the Joint⁷ Chiefs of Staff, said the first mission had taken place on Thursday but the drones had turned back due to bad weather.

He said the drones - which can fly at a lower altitude than conventional fighter jets - were "uniquely suited for urban areas", providing improved visibility of tanks and other potential targets.