Vice President Joe Biden
Vice President Joe BidenReuters

US Vice President Joe Biden on Wednesday visits Turkey for critical talks with its leadership seeking to repair strained relations following the failed July 15 coup and discuss defeating jihadists in Syria.

Biden will be by far the highest-ranking Western official to visit Turkey since the coup attempt to unseat President Recep Tayyip Erdogan.

The US number two is the only senior figure in the administration of President Barack Obama to have built a close personal relationship with Erdogan, after two face-to-face meetings in Turkey in the last two years alone.

But Biden will need all of his trademark charm and charisma for this visit, which is expected to see him strongly pressed by Turkish officials to extradite the US-based Islamic preacher Fethullah Gulen whom Ankara accuses of ordering the coup.

Washington has irritated Ankara by saying it needs to see evidence rather than allegations. Turkish officials have warned that US relations with the key NATO member will suffer if Gulen is not sent back home.

The coup bid led to a surge of anti-Americanism in Turkey with elements in the pro-government press and even a cabinet minister suggesting the United States had a hand in the coup.

Turkish Prime Minister Binali Yildirim acknowledged relations after the coup needed improving.

"Why is Mr Biden coming? To bring relations from medium to sweet," he said, using an expression usually applied to the sweetening of Turkish coffee.

"What's in Mr Biden's bag? There is the Syrian issue as well as Turkish-US relations," he added.

Biden is arriving at a crucial juncture in the over five-year civil war in Syria amid signs Ankara is willing to soften its stance that Syrian President Bashar al-Assad must go in order to resolve the conflict.

With the stranglehold of Islamic State (IS) jihadists in parts of northern Syria weakening, Biden will also discuss moves by Kurdish militia and Ankara-backed rebels to expel the IS militants from Syrian towns close to Turkey such as Jarabulus.

The United States backs the Kurdish People's Protection Units (YPG) militia as its main ally on the ground in Syria, but Turkey regards the outfit as a "terror group" bent on carving out an autonomous region in Syria.

Biden's visit is also taking place under the shadow of the devastating suicide bombing of a Kurdish wedding in Turkey's southeastern city of Gaziantep at the weekend that left 54 people dead, most of them under the age of 18.

Ankara backtracked on initial claims it was carried out by a child bomber acting on the orders of IS but press reports have said a jihadist link remains the main hypothesis.

Biden wrote on Twitter the main reason for his trip was to "underscore America's solidarity with the Turkish people in the wake of tragic attacks and coup attempt."