By Jeff Mason and Ece Toksabay
ANKARA (Reuters) - U.S. Vice President Joe Biden sought on Wednesday to ease tensions with Turkey over its demands for the extradition of a cleric it blames for last month's failed coup, saying Washington was cooperating but needed evidence to meet U.S. legal standards.
Speaking during a visit to Ankara, Biden's comments came hours after President Tayyip Erdogan said Washington had "no excuse" for keeping hold of Muslim cleric Fethullah Gulen, who has lived in U.S. exile since 1999.
The extradition demand for Gulen and Turkish perceptions of an unsympathetic Western response to the coup attempt have chilled relations between the United States and Turkey, a NATO ally and partner in the U.S.-led war on Islamic State.
"We have no ... interest whatsoever in protecting anyone who has done harm to an ally. None," Biden said. But the standards required under U.S. law must be met, he said.
Lawyers say the process could take years. Even if approved by a judge, an extradition request would still have to go to the U.S. Secretary of State, who can consider non-legal factors, such as humanitarian arguments.
After meeting Biden, Prime Minister Binali Yildirim said Turkey and the United States should never allow incidents to harm relations, but Ankara expected the legal process for the Gulen extradition without delay.
"If the extradition process of this terrorist leader could accelerate, if our cooperation on this matter continues like this, the Turkish people will quickly recover from their sadness and disappointment," the premier said.
Turkey blames Gulen's supporters for the coup that killed 240 people. The cleric, who lives in Pennsylvania, has denied the charge and condemned the coup.
The government has cracked down on suspected Gulen followers, detaining more than 40,000 people and formally arresting around half of them. About 80,000 people in the judiciary, police, civil service and elsewhere have been sacked or suspended.
Critics fear Erdogan is using the coup as a pretext to curtail dissent. Biden, who made strong statements on free speech and free expression on his last visit to Turkey, was less vocal this time.
Biden said that the prime minister, the foreign minister and others had made it clear they would adhere to constitutional principles and that the rule of law would prevail.
"Let's give them some time. I believe they mean what they say. And so let's move on," said Biden, who is due to meet Erdogan later in the day.
Ankara will probably send the United States a coup-related extradition request for Gulen next week, the Turkish justice minister said on Wednesday.
Shortly before Biden's arrival, Turkish forces launched a major operation inside Syria to clear Islamic State militants out of the Syrian frontier town Jarablus, backed by U.S.-led coalition warplanes.
But U.S.-Ankara relations have been complicated by that conflict. Washington backs the Syrian Kurdish YPG rebels against Islamic State. Ankara is worried the YPG's advance emboldens Kurdish insurgents in its mainly Kurdish southeast.
Washington has said it needs clear evidence to extradite Gulen. The U.S. State Department said this week that documents submitted so far by Ankara constituted a formal extradition request, although not on issues related to the coup.
Biden was guided by Turkish officials around the parliament, which was bombed during the coup attempt.
Rogue troops commandeered tanks, jets and helicopters to attack state institutions in Istanbul and Ankara in the failed coup bid that killed more than 240 people.
Turkish authorities fired more than 2,800 judges and prosecutors on Wednesday, in the latest purge related to the coup, broadcaster CNN Turk reported.
(Reporting by Ayla Jean Yackley and Ece Toksabay; writing by Patrick Markey; Editing by David Dolan and David Stamp)