SAYLORSBURG, Pa.—The reclusive cleric who was accused by Turkish President Recep Tayyip Erdogan of planning a coup attempt one year ago from his gated U.S. compound urged in a rare interview that the West stand up to what he called Turkey’s increasingly authoritarian leader.

In an ornate conference room in his home in the Pocono Mountains, the cleric Fethullah Gulen repeated his declaration that he has never been involved in any coup-plotting. He decried Mr. Erdogan for launching a purge within Turkey, the brunt of which...