By Karen Freifeld

NEW YORK (Reuters) - Former New York Mayor Rudy Giuliani, a one-time federal prosecutor, is joining U.S. President Donald Trump's personal legal team, Trump lawyer Jay Sekulow said in a statement on Thursday.

"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 quoted Trump as saying.

Giuliani was one of three attorneys Sekulow said were being added to the president's legal team dealing with Special Counsel Robert Mueller's investigation into Russian interference in the 2016 election.

Russia has denied meddling in the election. Trump has said there was no collusion and has called the Mueller probe a "witch hunt."

Sekulow also announced south Florida husband-and-wife white-collar defense lawyers Martin and Jane Raskin were joining the president's legal team.

The addition of Giuliani and the Raskins represents a major boost to Trump's legal firepower. The president has previously struggled to retain a top-flight criminal lawyer to represent him in the Mueller probe. Washington lawyer John Dowd, the most recent head of his team, resigned last month.

Giuliani had a storied career as a federal prosecutor before becoming mayor of New York in 1994 and achieved wide respect for his leadership when the city was attacked on September 11, 2001. But his often hard-bitten remarks in recent years, some made in support of Trump's candidacy, have drawn criticism.

Gerald Shargel, a retired New York defense lawyer who knows both Giuliani and Trump, said the former mayor would likely clash with Mueller.

The president's legal worries have recently expanded beyond the Mueller probe to include a criminal investigation in New York of Trump's personal lawyer Michael Cohen, whose home and offices were raided by the FBI on April 9.

The Republican mayor of New York from 1994 to 2001, Giuliani was also the chief federal prosecutor in Manhattan for much of the 1980s. During that time, he brought many high-profile cases targeting insider trading on Wall Street.

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Giuliani was also a top Department of Justice official in the Reagan administration. He ran unsuccessfully for the Republican nomination for president in 2008.

Since exiting the mayor's office, Giuliani has been in private practice, most recently at the law firm of Greenberg Traurig. The firm said Giuliani is on a leave of absence, effective today.

The Manhattan U.S. Attorney's Office, which is overseeing the Cohen investigation, is headed by Geoffrey Berman, a former law partner of Giuliani's at Greenberg Traurig.

(Reporting by Karen Freifeld; Additional reporting by Jan Wolfe; writing by Anthony Lin; editing by Lisa Shumaker and Diane Craft)