The criticism has not been uniform, with many national security specialists saying Mr Obama has had to juggle an unprecedented range of challenges in a brief period affecting longtime allies and foes.

Hillary Clinton, secretary of state, and Robert Gates, defence secretary, in joint TV appearances on Sunday, said the Libya action had succeeded in preventing a humanitarian catastrophe. But they resisted offering a time frame for ending US involvement – even as Washington hands over formal control to Nato – and also sought to distinguish Libya from other protest movements.

While deploring the bloodshed in Syria, Mrs Clinton said the situation did not warrant intervention because the level of violence was not the same as in Libya. “There’s a difference between calling out aircraft and indiscriminately strafing and bombing your own cities [like Libya], than