Asked if a stalemate was emerging in the seven-week-old conflict, the head of US Africa Command General Carter Ham said: "I would agree with that at present, on the ground."

He told a Senate hearing in Washington the US should not arm the rebels without a better idea of who they were and when asked how the war would end, said: "I think it does not end militarily."

There was little likelihood that rebels would be able to fight their way to Tripoli and oust Gaddafi by force, Ham said.

With daily skirmishes near the contested port of Brega in eastern Libya making little impact on the front line and rebels unable to end a brutal government assault on the western city of Misrata, NATO admits its mission to protect civilians is tough.