Former Democratic Vice President Joe Biden ripped President Donald Trump Tuesday as "a joke" — adding that his attacks on the FBI were "doing everything that Putin ever wanted."

"This is first president to make a full-throated, unvarnished attack on the entirety of the FBI," Biden, 75, the two-term vice president who retired in January after more than four decades in Washington, told Chris Cuomo on CNN.

"Not going after J. Edgar Hoover who was one person in the FBI," he added. "This is to discredit the FBI and discredit his own justice department.

"I spent a lot of time traveling around the world," Biden explained. "What do you think they're thinking in Moscow?

"This is doing everything that Putin ever wanted," Biden said, referring to Russian President Vladimir Putin. "Sowing doubt about whether or not our justice system is fair.

"Sowing doubt about whether or not there's anything remotely consistent with our constitution," he added. "It is a disaster."

Biden told Cuomo that he, too, would advise President Trump against talking with Russia special counsel Robert Mueller — as his lawyers reportedly have done — because "the president has some difficulty with precision."

"One of the things that I would worry about if I were his lawyer is him saying something that simply not true without him even planning to be disingenuous," Biden said.

"I just marvel at some of the things he says and does," he added, referring to Trump slamming Democrats as "treasonous" for not applauding during his remarks about the economy at his State of the Union address last week.

"He's a joke."