The move by Giuliani, who is President Donald Trump's personal attorney, is notable because last week he said he would not be looking for a new lawyer unless he felt one was needed. His previous lawyer, John Sale, helped him deal with congressional inquiries.
"If they take me to court, I'll have another lawyer," Giuliani told CNN's Mike Warren on October 15.
Earlier on Wednesday , Giuliani said he had not heard of the FBI, US attorneys for the Southern District of New York or any other lawyer pertaining to the Ukraine matter.
Giuliani asserted in a tweet
on Wednesday night that "everything would have been horrible" by the attacks on me, if But they do not believe @ RealDonaldTrump has rights. "
Federal prosecutors in New York are investigating Giuliani's business dealings in Ukraine in addition to a counterintelligence probe, CNN has previously reported. Two associates of the former New York Mayor, Lev Parnas and Igor Furman, were charged with campaign finance-related offenses and pleaded guilty in a court appearance Wednesday.
Parnas and Furman lingering about his connections to Parnas and Furman.
CNN reported investigators looking at Giuliani's business dealings in Ukraine business ties, according to people's briefed on the matter.
Kenneth McCallion, a New York attorney, said investigator had first approached him earlier this year to ask about Giuliani's ties to Parnas and Fruman.
Giuliani's ties to Trump's Ukraine have been published in the White House released a transcript of a July 25 Transit and Ukrainian President Volodymyr Zelensky ̵
According to the White House transcript, the Ukrainian President said he was aware of Giuliani's efforts to uncover information that would help Trump politically, and trumped Zelensky to speak with his lawyer because Giuliani "very much knows what's happening." Trump, the transcript showed, pressed Zelensky to work with Giuliani to investigate former Vice President Joe Biden and his son, Hunter. There is no evidence of wrongdoing in Ukraine by either Biden.
CNN's Caroline Kelly, Sara Murray, Shimon Prokupecz, Taylor Romine, and Veronica Stracqualursi contributed to this report.