Rudy Giuliani, President Donald Trump's personal lawyer, repeatedly pushed Trump to hand a controversial Muslim cleric living in the US over to Turkey, The Washington Post reported.

Turkish President Recep Tayyip Erdogan has accused the cleric, Fethullah Gulen, of orchestrating a failed coup against him in 2016 and of fomenting dissent within Turkey. Getting the US to extradite Gulen is a top priority for Erdogan.

Giuliani was reportedly so adamant in pushing for Gulen to be turned over to Erdogan that White House aides worried that he was working on behalf of the Turkish government.

Giuliani is not a registered foreign agent and is currently under investigation for violating lobbying laws related to his role in pushing for the ouster of the US's ambassador to Ukraine.

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President Donald Trump's personal attorney, Rudy Giuliani, privately pushed him to hand over a controversial Muslim cleric to Turkey, The Washington Post reported.

The cleric, Fethullah Gulen, lives in exile in Pennsylvania and has been accused by Turkish President Recep Tayyip Erdogan of orchestrating a failed 2016 coup against him and of generally fomenting dissent within Turkey. Gulen denies any involvement in the attempted coup.

Getting the US to extradite Gulen has long been a top priority for Erdogan, and Giuliani's reported efforts to facilitate that goal raises further questions about the extent to which he tried to influence government policy while acting as a private citizen.

The Post reported that Giuliani mentioned Gulen so often that one former official described the topic as the former New York mayor's "hobby horse."

"It was all Gulen," a second former official told the Post. Giuliani was so intent on the matter that some White House aides reportedly worried he was working on behalf of the Turkish government.

Trump's advisers were staunchly opposed to handing Gulen over to Erdogan, but The Post reported that the president was open to the suggestion and asked why he couldn't give Gulen over to Turkey and Erdogan, whom he referred to as "my friend."

Read more: The floodgates are opening as Trump officials publicly defy his orders and more whistleblowers come out of the shadows

Giuliani told The Post on Monday that he didn't need to register as a foreign agent because he never represented Turkey. On Tuesday, he declined to discuss the matter, telling the outlet in a text exchange that he "can't comment on it" because "that would be complete attorney client privilege but sounds wacky."

Giuliani is already under scrutiny for his ongoing efforts to push Ukraine's government to investigate former Vice President Joe Biden and his son for corruption.

The former New York mayor is also under federal criminal investigation, according to reports, over his role in the abrupt ouster of Marie Yovanovitch, the US's former ambassador to Ukraine, and whether Giuliani broke foreign lobbying laws in the process. Specifically, prosecutors are said to be examining whether Giuliani was working on behalf of the Ukrainian prosecutor general, Yuriy Lutsenko, while pushing for Yovanovitch's dismissal.

Yovanovitch, meanwhile, testified to Congress last week that she was recalled based on "unfounded and false claims by people with clearly questionable motives." She said she didn't know Giuliani's motives in attacking her but added that people associated with Giuliani "may well have believed that their personal financial ambitions were stymied by our anti-corruption policy in Ukraine."

The Post's latest revelations about Giuliani come as Turkey carries out a brutal assault on Kurdish forces — one of the US's closest allies in the fight against ISIS — in northeast Syria after Trump abruptly pulled troops from the region following a phone call with Erdogan.

Giuliani was also involved in an unsuccessful attempt to get then Secretary of State Rex Tillerson to help stymie the Justice Department's investigation into a Turkish-Iranian trader.