The Turkish prime minister made the announcement in an answer to a reporter's question following a meeting of lawmakers from his AK Party on Tuesday.
Asked whether he intended to start the formal process of seeking Gulen's extradition from the United States, Erdogan responded: "yes, it will begin."
The statement came just hours after Erdogan used a television interview to suggest that Gulen posed a threat to the United States.
"These elements which threaten the national security of Turkey cannot be allowed to exist in other countries because what they do to us here, they might do against their host," Erdogan told PBS television, according to a transcript issued by the US public broadcaster.
Erdogan and Gulen have been at loggerheads since last December, when police raids led to the detention of dozens of Erdogan's political and business allies on allegations of corruption. Erdogan responded by firing thousands of police officers and prosecutors. In a further measure, the government also banned the micro blogging website Twitter, but this was later overturned by a court.
He has accused Gulen, who runs a network of businesses and schools from self-imposed exile in the US state of Pennsylvania, of masterminding the corruption scandal. Gulen has denied this, but he has been a vocal critic of the Turkish government, particularly for its police and judiciary purge.
Gulen has lived in the United States since 1997, when accusations of Islamist activities were raised against him in Turkey.
pfd/hc (Reuters, AFP)