WASHINGTON (AP) — A Russian billionaire with ties to Vladimir Putin sued The Associated Press on Monday for defamation over a story about his connections to a former Trump campaign chairman.

Aluminum magnate Oleg Deripaska claimed in the federal defamation and libel lawsuit that the AP's March 22 story about his business dealings with Paul Manafort was inaccurate and hurt his career by falsely accusing him of criminal activity.

The AP's general counsel, Karen Kaiser, said the news organization stands by its story and will defend itself vigorously.

The AP reported that before signing up with Donald Trump, Manafort secretly worked for Deripaska with a plan to "greatly benefit the Putin government."

The story was based on interviews with people familiar with payments to Manafort and business records obtained by the AP. Those records included strategy memoranda and records of international wire transfers for millions of dollars.

The story said Manafort proposed as early as June 2005 that he would influence politics, business dealings and news coverage inside the United States, Europe and former Soviet republics to benefit President Vladimir Putin's government. Manafort pitched the plans to Deripaska, an aluminum magnate and close Putin ally with whom Manafort eventually signed a $10 million annual contract beginning in 2006. The story said how much work Manafort performed under the contract was unclear.

The story said Manafort and Deripaska maintained a business relationship until at least 2009 but noted the two later had a falling out laid bare in 2014 in a Cayman Islands bankruptcy court.

After the AP story was published, Deripaska purchased advertisements in U.S. newspapers calling the reporting a "malicious assertion and lie," saying he never made any commitments or contracts to covertly promote or advance Putin's interests. He also said he was willing to take part in U.S. congressional hearings to discuss his past business relationship with Manafort.