US Vice President Joe Biden visited Turkey on August 24, seeking to ease heightened tensions after last month’s coup attempt, but failed to give any encouragement on the extradition of US-based cleric Fettullah Gulen, who Ankara says was the coup's mastermind.

Biden visited the parliament building that was bombed during the coup attempt and he held talks with President Recep Tayyip Erdogan and Prime Minister Binali Yildirim.

The vice president apologised for not coming to Turkey earlier, and reassured Turkish leaders of US support for the government. He also pleased Ankara by calling for the Syrian Kurdish PYD guerillas to pull back across the Euphrates, but his comments regarding the possible extradition of Gulen were disappointing.

Ankara accuses its Western allies, including the US, of failing to show enough support for the elected government during and after the botched coup.

Western leaders have criticised the Turkish government’s wide crackdown on the alleged perpetrators of the coup attempt and urged Ankara to respect the rule of law. But Turkey says its allies are underestimating the threat that supporters of Gulen pose to the country.

In the wake of the coup attempt, Turkey immediately demanded the extradition of Gulen who has been living in the US since 1999.

Animosity against the US has risen sharply in Turkey after the putsch. For one thing, in the eyes of many Turks America is harbouring a traitor. There are wild speculations among the public that the US might have been been complicit or even have supported the coup.

Washington, however, says the extradition is purely a legal issue and Biden conveyed this message strongly during his visit to Turkey.

“We are cooperating with Turkish authorities, our legal experts are working right now with Turkish counterparts on production of and evaluation of material and evidence that needs to be supplied to an American court to meet requirements under our law and the extradition treaty,” Biden said in Ankara.

“We have no interest whatsoever in protecting anyone who has done harm to an ally, but we need to meet legal standard requirements under our law,” he told reporters, adding that the president has no authority to extradite anyone on his own power, only an American court can do that.

Biden’s comments fell short of Turkey’s expectations. Erdogan told reporters that the extradition of Gulen was a priority and Turkey’s demands should not be disregarded.  “Bilateral agreements between Ankara and Washington at least require his detention”, he told reporters after the meeting, stressing his disappointment.

It is clear from these comments that the Gulen affair will continue to haunt Turkey-US relations in the period ahead and it is difficult to predict how it could be resolved.

At the same time, the two countries are working together in Syria, which the US will hope provides the foundation for improved relations.

At the press conference in Ankara, Erdogan announced that Turkish-backed Syrian rebels have retaken the town of Jarablus in Northern Syria, just across the border, from Islamic State (IS).

After 4am on August 24, the Turkish military and its warplanes started to pound IS positions in and around Jarablus. The Free Syrian Army (FSA), backed by Turkish tanks and armoured vehicles, then crossed the border into Syrian territory and within hours the town fell to the Syrian opposition group.

Biden voiced support for Turkey and said the US was providing air cover for the military operation -dubbed Euphrates Shield.

The Syrian government has condemned the military operation, labelling it “a blatant violation of its sovereignty”, while Moscow said it is deeply worried over the events on the Turkish-Syrian border.

Officials at Ankara say the objective of the military operation is to clear the Turkish borders of terrorist groups, helping to enhance border security and support the territorial integrity of Syria. Erdogan has clearly said it also aimed against the Kurdish Democratic Union Party (PYD), which has captured swathes of northern Syria from IS, as much as IS  itself.

The Syrian Kurdish group’s advances in Northern Syria are seen as a threat by Turkey, which sees the PYD and its military unit YPD as an extension of the Kurdistan Workers’ Party (PKK), which has been fighting a guerilla war inside Turkey for decades.  

A YPG-led group recently captured the town of Manjib near Jarablus, stoking fears in Ankara that the Syrian Kurds may soon establish a state along Turkey's border by linking the areas controlled by the PYD on the east and west banks of the Euphrates River.

The advance also raises the risk of a potential conflict between the PYD and the FSA supported by Turkey. Ankara says the PYD-YPG must pull back to the east of the Euphrates. 

The US backs the PYD-YPG in the fight against Islamic State in Syria but Biden said that Turkey's border must be controlled by Turkey, and there should be no occupation by any other group. He backed Ankara’s call for the PYD to retreat to the east of the Euphrates River, saying that US support for the Kurdish group would be stopped if it didn’t comply.

However, YPG spokesperson Redur Xelil has said the Kurdish force will not retreat from the west of the Euphrates. “We are in our own country and not withdrawing on the request of Turkey or someone else," Xelil said.

“Any military confrontation between the PYD and the FSA-led forces supported by Turkey would severely strain Ankara’s already very tense relationship with Washington,” Wolfgango Piccoli at Teneo Intelligence said in a comment on August 24.