Former New York City Mayor and U.S. Attorney Rudy Giuliani has joined President Trump's personal legal team that is aiding Mr. Trump in special counsel Robert Mueller's investigation into Russian election meddling and any ties to Trump associates, CBS News' chief White House correspondent Major Garrett has confirmed.

Sekulow said in a statement that the president welcomed the news, and quoted him, saying, "'Rudy is great. He has been my friend for a long time and wants to get this matter quickly resolved for the good of the country.'"

Sekulow added that he has worked with Giuliani for many years and the team welcomes his expertise. He also announced the addition of two other attorneys, Jane Serene Raskin and Marty Raskin, both former federal prosecutors.

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Giuliani will join Ty Cobb and Jay Sekulow, who are already on Mr. Trump's team who are left on Mr. Trump's legal team as attorneys have come and gone. In recent weeks, John Dowd has left Mr. Trump's legal team, Joe diGenova was looking to join the team but ultimately did not. Before he departed, Dowd called for an end to the Russia probe, something Giuliani also appears to want to happen.

"I'm doing it because I hope we can negotiate an end to this for the good of the country and because I have high regard for the president and for Bob Mueller," Giuliani told the Washington Post, which first reported he is joining Mr. Trump's legal team.

Giuliani's entrance also comes as sources close to another attorney of Mr. Trump's, Michael Cohen, fear Cohen could flip on the president, after raised on Cohen's home, office and hotel room, CBS News' Jeff Pegues has reported.

In 2016, Giuliani appeared to be vying for the job that now belongs to Jeff Sessions — attorney general. In November 2016, Giuliani told CNN, "there's probably nobody that knows the Justice Department better than me."

Before the 2016 presidential election, Giuliani called Mr. Trump a "flawed human being," after the "Access Hollywood" tape emerged in which Mr. Trump made lewd remarks about women.

Giuliani is painted in an unflattering light in fired former FBI Director James Comey's new book, "A Higher Loyalty." Comey, who is on a tour for his book this week, describes the former NYC mayor as someone who craves attention and has a problematic ego.

Giuliani was mayor of New York during the Sept. 11, 2001 attacks.