Former President Donald Trump's attorney Rudy Giuliani is facing a federal inquiry over possible improper lobbying for Turkey, a source familiar with the matter told ABC News.

       The Justice Department's inquiry is separate from the criminal investigation into Giuliani's activities in Ukraine, the source said.

       Giuliani's actions first raised questions in 2017 when he was hired to represent Turkey-based, Iranian-born businessman Reza Zarrab in a money laundering and sanctions evasion case brought against Zarrab by the U.S. attorney in the Southern District of New York.

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       Giuliani personally urged then-Secretary of State Rex Tillerson to drop the case during a 2017 oval office meeting, sources told ABC News at the time. Zarrab eventually pled guilty to the charges.

       Bloomberg via Getty Images, FILE

       Rudy Giuliani, personal lawyer to President Donald Trump, speaks to members of the media following a television interview outside the White House, July 1, 2020.

       Sources also said at the time that Giuliani urged the administration to deport exiled cleric Fethullah Gulen, whom Turkish President Erdogan accused of inciting a coup.

       An attorney for Giuliani could not be reached for comment, but the former New York City mayor has previously denied any wrongdoing.

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       A spokesperson for the Justice Department declined to comment, as did a spokesperson for the U.S. Attorney’s Office for the Southern District of New York.

       It wasn’t immediately clear when this inquiry, first reported by Bloomberg, began.