AS THE Syrian ceasefire arranged by the United States and Russia teeters on the brink of collapse, it's clear the main problem lies in Washington.
Moscow's goal has never been in doubt: it wants the regime of Bashar al-Assad to survive. The Obama administration has been reluctantly moving towards the same conclusion but it simply can't admit it, even to itself.
The Russian government bitterly condemned the American air strike that killed 60 to 80 Syrian army personnel on Saturday, but everybody knows that air strikes sometimes hit the wrong people. It was a mistake, that's all, and the Russians really understand that -- but it was a mistake that tells us a lot about how far the US has moved.
Until recently the US, still formally pledged to overthrow the Assad regime, would not attack Islamic State troops if they were fighting the Syrian army. (That's why Islamic State captured the historic city of Palmyra two years ago: the US air force would not strike the long and vulnerable Isis line of communications across the desert, because that would have been "helping Assad".)
But the US air attack that went astray at Deir es-Zor last weekend was targeting Isis troops who were in direct contact with the Syrian army. It's because the two sides were so close together that the planes hit the Syrian troops by mistake. American diplomats still deny it, but the US is now willing to help Assad, at least sometimes.
The strategic calculation that has driven US Secretary of State John Kerry into this uncomfortable position is brutally simple. If Assad's regime does not survive, then the extreme Islamists will take over all of Syria. The fantasy of a "third force" in Syria, made up of democracy-loving non-Islamist rebels who could defeat both the Islamists and Assad, has died even in the US State Department and the Pentagon.
The "moderate" rebels that the US has backed for so long make up no more than 10 or 15 per cent of the real fighting strength of the anti-Assad forces, and most of them are actually allied to the Islamists. In fact, the "moderates" wouldn't survive long without their Islamist alliance -- so it's time for Washington to abandon them.
The ceasefire terms show that Kerry has implicitly accepted that logic, for they demand that the Syrian government and the "moderates" stop shooting and bombing, whereupon the American and Russian air forces will co-operate in bombing the Islamists. And the targets will not only be Isis but also the al-Qaeda-linked group that was known until recently as the Nusra Front.
Unfortunately, the "moderate" groups are not only in close alliance with Nusra but are physically mixed in with the Islamist forces. They will get bombed too if they do not break their links with the Islamist extremists and move away from them, so the ceasefire co-sponsored by the US and Russia demands that they do exactly that. Unfortunately, they can't.
They can't do it because on their own they could never hope to overthrow the Assad regime -- and also because the Islamists will start killing them as traitors if they even try to break away. So the "moderates" haven't really accepted the ceasefire either, and the Russians are quite right to complain that they have "not met a single obligation" of the truce.
Everything we know about the ceasefire argues that the Obama administration has accepted the necessity of leaving the Assad regime in power, although it still cannot bring itself to say so publicly.
�Gwynne Dyer is an independent journalist whose articles are published in 45 countries.