Joe Biden reassured Ankara, but it is unclear how Washingtons Kurdish proxies will react to his demand that they step back

Turkish tanks moved rapidly through the Syrian township of Jarablus on Wednesday, ousting the Islamic State terrorist group from one of its last perimeter strongholds but the most important outcome in Ankaras eyes was trumping the US-backed Kurdish fighters in a race to seize the surrounding area.

In a pointed concession to Turkey, Joe Biden demanded that Kurdish forces-out, who had been a central US proxy in the fight against the terrorist group, move back across the Euphrates river, to the east of Jarablus. The US vice-president also said that the Kurds, who have won a series of recent battles against Isis, would be abandoned if they advanced. US planes dedicated cover to the Turkish move, one of the first times in the war that the two friends have conducted a joint operation.

They cannot, will not, under any circumstance get American support if they do not keep that commitment, Biden said in Ankara during a visit to reset ties with Turkey, which had been strained since the failed takeover attempt in July.

The Turkish incursion, which was supported by Syrian rebels, was the largest into Syria in the five-year civil war and came as months of gains by Kurds in the north which had seriously tested the relations with Washington and transformed the once-dormant perimeter into one of the wars most important battle zones.

Bystanders throughout much of the war, Kurdish groups in Syrias north-east had constructed swift gains after Russias intervention to reinforce President Bashar al-Assad. At the same period, the Kurds had been pivotal to US efforts to break the grip of Isis in the area, being used as a proxy force by US trainers and given air support by fighter jets.

The development incensed Ankara, which insists that the Kurds were employing the war to advance a de facto autonomous areas aligned with the aims of a four-decade-long revolt being waged by Kurdish groups in Turkeys south-east. Turkish officials have repeatedly pointed to Kurdish maneuvers along its 500 -mile frontier as proof of a plan to move Arabs from the area and create a buffer permitting the Kurds to consolidate influence in the area.

In recent months, Turkey has stepped up its support for Syrian rebels combating both Isis and the Assad regime. The influence of rebel groups in the north has hitherto waned under Russian airstrikes and the crawling of jihadi groups, who had gradually taken the dominance in key campaigns, such as the fight for Aleppo.

A Turkish move to re-arm Syrian rebels, including jihadis, earlier this month had led to the siege of Aleppo imposed by Assad loyalists being broken and a furnish line being reopened.

Since then, Turkey has stepped up efforts to deter the Kurds from building move forward with and to keep open access to Arab rebel areas.

At the same time, Ankara has set aside a feud with Russia, which shares its insisting that Syrias current borders be preserved. Recent public statements about talking to the Syrian regime give weight to a growing position in the region that Turkey opinions keeping Syria intact as a higher priority than removing the Syrian leader a key goal of the Turkish leadership for the past five years.

Bidens demands that the US-backed Kurds go no further is likely to reassure Ankara, which had publicly denounced Washingtons endeavors against Isis, even as a Kurdish-led force, comprised of some Arab divisions, pushed Isis from the city of Minbij earlier this month, splintering a furnish line between the town of al-Bab, near Aleppo, and Raqqa to the east, which remains one of the groups two most important hubs.

However, the effect on the US-Kurdish relationship is less clear. The Syrian Kurdish political extremity, the PYD, said in response to the campaign that Turkey will be defeated just like[ Isis ].

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