Two weeks after a dark-of-night barrage of mostly US missiles and bombs opened the international air assault on Libya’s Muammar Gaddafi, the American combat role is ending, the ragtag rebels are reeling and the Pentagon is betting its European allies can finish the job.

Gaddafi is still standing, with a few uncertain signs that his inner circle could crack. The Obama administration is hoping that, if Gaddafi’s government doesn’t implode soon, a relentless campaign of air strikes on his tanks, air defences and most trusted army units will at least weaken his ability to survive a renewed uprising by a disjointed opposition. The rebels initially rattled Gaddafi but in recent days have given up most of their gains.

So the mission remains incomplete, but the US is following through on a pledge to shift the main combat burden to Britain, France and other NATO allies.

Starting yesterday, no US combat aircraft are to fly strike missions in Libya. NATO’s on-scene commander can request American strikes in the days ahead, in which case they may have to be approved in Washington.

On Saturday, US combat aircraft flew 24 strike missions in Libya, the Pentagon said.

Also withdrawing from the combat mission yesterday were the initial workhorses of the military campaign: US Navy destroyers and submarines that launched Tomahawk cruise missiles from their positions in the Mediterranean Sea.

The US planes and naval vessels will be on standby in case NATO commanders decide their forces cannot handle the mission on their own. Combat air missions will continue to be flown by Britain, France and other NATO member countries.

A larger group of participating air forces will patrol over Libya to ensure that Gaddafi’s air force stays grounded. US planes will support them with refuelling aircraft and electronic jammers.

The US Navy began the operation on 19 March with 12 ships in the Mediterranean. As of Friday, nine remained.

The international military mission has been limited from the start, with the stated objective of protecting Libyan civilians from attack. But until this weekend’s US stand down, Air Force and Marine attack planes have chased down Libyan tanks and other targets on a daily basis.

Still to be decided is whether the White House will up the ante and provide arms to the rebels. That step, say some congressional supporters of the Libya mission, is crucial to ensuring that the strategic goal of ousting Gaddafi is achieved before he kills still more opponents.

On the political front, the US and its allies are hoping that the defection to Britain on Wednesday by Libyan Foreign Minister Moussa Koussa is a sign of things to come.