THE United States’ “exclusion zone” in northern Syria, apparently designed to protect US special forces embedded with Kurdish People’s Protection Units (YPG) from Syrian bombers, marks a dangerous new phase of this nightmarish war.

However much the US denies it is creating a no-fly-zone, threats to shoot down Syrian or Russian aircraft that come too close certainly make it sound like one.The fact that the YPG evidently asked for such assistance highlights the breakdown in relations between it and the Syrian government, for years effective allies in their joint struggle against Isis terror.

Turkey’s attitude to the raging conflict across the border has changed dramatically since July 15’s failed coup against President Recep Tayyip Erdogan.

Erdogan is convinced that his Nato ally the United States was party to the attempted military putsch, or at least aware of it in advance.

That his former adversaries in Russia and Iran tipped him off about the threat has helped lubricate his Damascene conversion.

Turkey has promised to secure its border to finally end the flow of radical foreign jihadists into Syria, which is undoubtedly a welcome development.

And if Turkey, formerly a key bankroller and equipper of the extremist revolt, begins to co-operate with Syria, Russia and Iran in crushing Isis and the other terrorist outfits at play — groups such as Jabhat Fateh al-Sham, the new name for the al-Qaida affiliated Nusra Front — then the total defeat of these repulsive organisations may at last be on the cards.

But Turkey remains obsessed with crushing any prospect of an autonomous Kurdish region in Syria, especially one run by the YPG, close allies of the Kurdistan Workers Party (PKK) which is at war with the Ankara government.

Recent advances by the YPG into towns with mixed Arab and Kurdish populations such as Hassakeh look like a bid to build a corridor to Kurdish regions in Iraq, although authorities in Iraq’s autonomous Kurdistan Region have distanced themselves from any such project.

Rojava’s declaration of autonomy in March was hastily rejected as null and void by the Syrian authorities. Perhaps too hastily, since accommodating the legitimate aspirations of the country’s Kurdish community might have helped avoid recent developments.

A cross-border Kurdish-ruled region is a far greater threat to Syria’s territorial integrity than mere autonomy — and Damascus is predictably determined to stop it happening.

In that ambition it is joined by Turkey and Iran, fearful of the influence of such a statelet on their own Kurdish communities — which in both cases have been subject to harsh persecution for decades.

But it is opposed by the United States, which appears to back the idea of a breakaway Kurdish state which would fragment and weaken its rivals in the region.

This is presumably why the US has been arming and equipping the YPG, despite the Kurdish militia, like its PKK allies, being a product of the political left with a long history of opposition to US imperialism.

Whatever their differences, the struggle to defeat Isis is not advanced by a tragic and unnecessary armed conflict between the YPG and the Syrian army.

Attempts to broker a ceasefire between the sides should be supported, with preliminary Russia-mediated talks between Iran, Syria, Hezbollah and the YPG suggesting all sides could withdraw to their positions before the current fighting erupted.

In the longer term, attempts to carve out a Kurdish state from Syria, Iraq, Iran and Turkey are a recipe for decades of conflict.

But the YPG, with its commitment to secularism and championing of equal rights for women and men in a region scarred by medievalist bigotry, has earned its place at the table. Syria should not connive at a Turkish scheme intent on denying freedom and autonomy for the Kurdish people of both countries.