The United States is abandoning its train-and-equip programme aimed at producing over 5,000 rebels to fight in Syria, according to sources travelling with US defence chief Ash Carter.

Mr Carter, however, says it is merely being overhauled.

Either way the programme has been a disaster that a single-celled amoeba could have predicted was doomed from the start.

The idea of training men who could be sent into battle with modern weapons, liaising with US and allied airstrikes, with an understanding of operational security and a loyalty to the secular instincts - which, in part, drove the Syrian revolution in the first place - seems pretty straightforward.

But here's where the plankton-like blob would run up a red flag: trainees were told they would not be allowed to fight the regime of Bashar al Assad.

Instead they would only be allowed to fight the so-called Islamic State.

Small wonder that almost all of the trainees - most of whom were already battle hardened by years of fighting - simply walked out of the camps set up in Turkey.

Less than 60 graduated in the first batch out of several hundreds, and the programme that had a budget of $500m (£326m) a year has so far likely cost the US more than a million dollars (£653,000) per fighter.

The scheme was utterly doomed from day one, and it gets worse.

The small number who were trained, mostly ethnic Turkmen, entered Syria close to an area controlled by Jabhat al Nusra, an al Qaeda affiliate that is regularly bombed by the US but among the most effective units fighting Assad.

Al Nusra promptly kidnapped most of them.

The next batch to enter Syria did not wait to be hooded and hog tied - they simply turned up with their modern weapons and defected to various Islamist factions fighting Assad.

Syria's rebels detest the so called IS - even al Nusra is its sworn enemy - but they hate the Assad regime even more and have long argued they would fight both, but Assad first and then the extremist death cult.

The United States' desire to not only prioritise IS as the main enemy but also to ban its warriors from taking on Assad is incomprehensible, so much so the CIA stayed away from it altogether.

The agency has instead worked covertly alongside, if not hand in glove with, several other regional powers such as Turkey, Qatar and Saudi Arabia to nurture fighters from the Free Syrian Army who are already inside Syria fighting Assad.

Meanwhile, other allies have moved closer to more Islamist groups, but all have started to work well together in alliance with or as part of the Jaish al Fatah (Army of Conquest).

Lately they have been bombed by Russia and have fought hard against a new Syrian government ground offensive.

The American-made TOW tank-killing missiles they've been supplied have proven critical in their defence against a new onslaught planned jointly by Iran, Russia and Damascus.

If the Pentagon abandons this covert support it might as well give up having any Arab allies in Syria.