• Former New York City Mayor Rudy Giuliani is suing President Joe Biden for defamation.
• Giuliani said Biden's comments on the campaign trail labeling him a "Russian" pawn cost him law clients and a portion of his podcast audience.
• Giuliani previously was the personal attorney for former President Donald Trump.

WASHINGTON — Rudy Giuliani sued President Joe Biden for defamation Wednesday, saying he lost clients and podcast listeners after Biden called him a "Russian pawn" during an October 2020 debate with then-President Donald Trump.

Giuliani said he had not yet calculated how much he would seek in monetary damages from Biden and the campaign and fundraising committees that also are named in the complaint in Merrimack County Superior Court in Concord, New Hampshire.

"You can do that later. But it's in the millions and billions of dollars," said the former New York City mayor at a press conference outside the court.

The White House did not immediately respond to CNBC's request for comment about Giuliani's lawsuit.

Giuliani previously served as Trump's personal lawyer. He played a leading role in promoting false claims that Trump lost the 2020 election to Biden only as a result of widespread ballot fraud.

His suit against Biden comes a week after the president's son, Hunter Biden, sued Giuliani for alleged violations of computer fraud and data access.

Weeks before the 2020 election, Giuliani gave the New York Post a purported copy of Hunter's laptop computer. He and other Trump allies claim the laptop contains proof of Hunter Biden's allegedly corrupt business dealings in Ukraine.

Giuliani's new lawsuit mentions the laptop.

During his Oct. 22, 2020, debate with Trump, Joe Biden said, "Buddy, Rudy Giuliani, he is being used as a Russian pawn, he is being fed information that is Russian that is not true," Giuliani's suit noted.

Later in the debate, Joe Biden said the laptop contained Russian disinformation.

"Four, five former heads of the CIA say that what [Trump] is saying" about the laptop "is a bunch of garbage," Biden said. "Nobody believes it except … his good friend Rudy Giuliani."

At Wednesday's press conference, Giuliani said, "Being called by the leading candidate of the Democratic Party, [a] facilitator of Russian disinformation, is an extraordinarily damaging thing."

His suit says, "The Hunter Biden laptop contained no Russian information but rather contained the accurate, depraved, and revealing entries of someone engaged in influence peddling but also in throes of a drug addiction, and thereby revealing conduct and actions that at the very least would have cost Defendant Biden the 2020 presidential election if he had not lied about them and defamed the Plaintiff in the process of doing so."

In August, Giuliani was indicted with Trump and 17 other defendants in Atlanta state court on racketeering charges accusing them of conspiring to illegally attempt to overturn Trump's loss in the 2020 Georgia presidential election to Biden.