The State Department specified the formal extradition request for the FETO network leader was not linked to last month's coup attempt in Turkey.
The United States has received a formal request from Turkey for the extradition of Fethullah Gülen, the Pennsylvannia-based cult leader sought by Ankara for masterminding last month's deadly coup attempt.
"We can confirm now that Turkey has requested the extradition of Mr. Gülen. But I wouldn't characterize the request as relating to the coup attempt," deputy State Department spokesman Mark Toner told reporters at a press briefing.
"We have received a formal extradition request, just not one pertaining to the coup attempt," the spokesman added, declining to specify further.
Gülen has been living in self-imposed exile in the US since 1999 and heads the Fethullah Terrorist Organization (FETO), the group which Turkey has repeatedly said was behind the coup attempt. The failed putsch resulted in the deaths 240 people and injured over 2,000.
Ankara submitted a request for the extradition of Gülen on July 19, only days after the coup attempt. Toner revealed on Tuesday that the decision to accept the request formally was made "in the past several days".
US authorities said they were reviewing documents sent by Ankara and have insisted on seeing "all evidence" before considering the extradition request. Turkey and the US are party to a 1979 extradition treaty.
Toner's statement comes on the eve of US Vice President Joe Biden's visit to Turkey on Wednesday.
A separate delegation from the US arrived in Turkey on Monday to discuss the extradition of Gülen and it is unclear whether Biden would also be holding talks on the matter.
According to Biden his visit would 'underscore America's solidarity' with Turkey after a series of terrorist attacks in the country.
This week, I'll travel to Ankara to underscore America's solidarity with the Turkish people in the wake of tragic attacks and coup attempt.— VP Biden (Archived) (@VP44) August 22, 2016
Barbaric attack on a wedding using a child to kill more than 50, 29 of whom are kids. Another 66 injured. We stand with our Turkish allies.— VP Biden (Archived) (@VP44) August 22, 2016
During his visit, Biden will meet with Turkish President Recep Tayyip Erdoğan and Prime Minister Binali Yıldırım in separate meetings.
His visit to Turkey will be the highest level meeting between officials of the two countries following the failed coup attempt and tensions between Ankara and Washington over the extradition of Gülen.
Biden's spokesman Josh Earnest said, "That is a coup attempt that was roundly and publicly condemned by the United States government and we continue to strongly support the democratic government of our allies in Turkey."
According to Earnest, efforts to extradite Gülen would be governed by "an extradition treaty that's been on the books between the US and Turkey for more than 30 years."
Sources from the Turkish Justice Ministry, who spoke on condition of anonymity, said that three officials from the US Justice Department and another from the State Department arrived in capital Ankara late Monday night.
The delegation had already begun talks with officials from Turkey's Justice Ministry's International Law and Foreign Affairs Directorate on Tuesday morning.
Turkish officials are expected to share information about four different files dealing with the extradition of Gülen who is also accused of leading a long-running campaign to overthrow the state through the infiltration of Turkish institutions, particularly the military, police, and judiciary.
Turkey's government has repeatedly said the failed coup was also plotted by followers of Gülen and his Fethullah Terrorist Organisation (FETO).
Gülen has denied all the allegations.