Erdogan made the comment in a live interview with broadcaster NTV.
Andrew Brunson, who has lived in Turkey for more than two decades, was indicted on charges of helping the group that Ankara holds responsible for the failed coup against Erdogan. He faces up to 35 years in prison. Brunson denies the charges.
Erdogan has previously linked Brunson's fate to that of the cleric Fethullah Gulen, the Muslim cleric Turkey blames for the coup attempt. Gulen has lived in the United States since 1999 and denies the charges. Turkey is seeking his extradition from the United States.
U.S. President Donald Trump and dozens of U.S. senators have urged Erdogan to release Brunson.
(Reporting by Ali Kucukgocmen; Writing by David Dolan; Editing by Gareth Jones)