Ibrahim Kalin urged the U.S. to not allow Gulen to “exploit its laws to avoid facing a fair and legitimate accounting in Turkey,” in an opinion piece published in The New York Times.

Kalin wrote that mounting evidence has surfaced that points to Gulen leading the attempt, noting that the coup “was planned and staged by his followers within the army.”

Several generals and officers involved have confessed to having links to Gulen.

Levent Turkkan, aide-de-camp to the chief of staff for the Turkish armed forces, Gen. Hulusi Akar, admitted that he was a member of the Gulenist organization and joined the coup on order from his superiors within the group, according to Kalin.

Akar reportedly told prosecutors coup plotters urged him to speak to Gulen, who lives in the state of Pennsylvania, to persuade him to join the overthrow attempt.

“The United States should extradite Fethullah Gulen, a Turkish citizen, to Turkey, as is allowed under an existing treaty,” Kalin said. “Turkey has already provided a number of legal documents to American authorities and will send more as further evidence is collected.”

U.S. officials announced last week receipt of extradition documents for Gulen, following the coup attempt that killed more than 240 people and wounded more than 2,000 others.

The Justice Department is reviewing the papers, according to the White House.

Anadolu Agency