Former New York Mayor Rudolph Giuliani said Thursday he was joining President Donald Trump's legal team to try to end Russia special counsel Robert Mueller's probe "for the good of the country."

"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 in an interview.

Giuliani, 73, a former federal prosecutor and longtime Trump ally, said he formalized his decision in recent days, and had dinner with the president last week at the Mar-a-Lago resort in Florida.

He joins Trump's current team of personal attorneys, Jay Sekulow and Ty Cobb, and told the Post he soon would take a leave from his New York-based law firm, Greenberg Traurig.

In a statement from Sekulow to Reuters, the lawyer quoted President Trump as 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's statement also said two other lawyers were joining Trump's legal team, the white-collar defense lawyers Martin and Jane Raskin, a husband-and-wife team based in South Florida.

Giuliani once served as U.S. attorney for the Southern District of New York, the office that is currently overseeing an investigation into Trump's personal attorney, Michael Cohen.

The Daily Beast reported earlier Thursday that Giuliani was in talks to join President Trump's team.

In his Post interview, Giuliani declined to say whether Trump had decided on whether to sit for an interview with Mueller's investigators.

"It's too early for me to say that," Giuliani said.

He also declined to discuss whether Deputy Attorney General Rod Rosenstein, who appointed Mueller and oversees the Russia investigation, might soon be fired by Trump.

"I'm not involved in anything about those issues," Giuliani said. "My advice on Mueller has been this: He should be allowed to do his job. He's entitled to do his job."

Giuliani told the Post he would spend a "great deal of time" in Washington working with Trump, but would continue to live in New York.

He endorsed Trump's candidacy in 2016 at the Republican National Convention in Cleveland, though he was not selected for a Cabinet post by the president.

Termed "America's Mayor" because of his leadership during the 9/11 attacks, he was under consideration by Trump to replace Attorney General Jeff Sessions, Axios reported last summer.