The United States is evaluating new documents sent by Turkey to push for the extradition of US-based cleric Fethullah Gulen, the alleged mastermind of the country's recent failed coup, a State Department spokesman said on Thursday.

"The Turkish authorities (made) several deliveries of documents to us and we're in the process of going through those documents," spokesman Mark Toner told a daily news briefing.

Toner said the first batch "did not, we believe, constitute a formal extradition request."

He added: "We subsequently received more documents. We're looking through them ... and I don't think they've reached that determination yet."

The US Justice Department is the main agency poring over the documents to see whether they amount to a formal extradition request for Gulen, who has lived in self-imposed exile in Pennsylvania since 1999.

Turkish officials, including Foreign Minister Mevlut Cavusoglu, have warned that ties with the United States will be affected if it fails to extradite Gulen.

The NATO member plays an important role in the US-led fight against Islamic State. But Washington has said Ankara must provide clear evidence of Gulen's involvement in the failed military coup before any extradition process can move forward.

Gulen has denied plotting against Turkey and has condemned the coup attempt.

Toner said the United States had offered to help Turkey with investigating the coup. He did not say whether Turkey had responded to the offer.

Turkish President Tayyip Erdogan accuses Gulen of orchestrating the failed putsch and harnessing an extensive network of schools, charities and businesses in Turkey and abroad to infiltrate state institutions.

Erdogan vowed on Thursday to choke off the businesses, while an Istanbul court issued an arrest warrant for Gulen for "giving the instructions" for the coup attempt, in which more than 230 people were killed.

In New York, Kamil Aydin, a Turkish member of parliament from Erzurum, said the US Justice Department had received 85 boxes of documents from Turkey related to Gulen so far.

"They are in the process of evaluating these documents," he said, without giving any details on the files.