Jared Kushner confirmed that President Donald Trump was the subject of at least one extortion attempt during the 2016 election campaign.

The president's son-in-law and White House senior adviser released an 11-page statement Monday morning ahead of his closed-door hearing with the Senate Intelligence Committee detailing his contacts with Russian officials during the campaign and transition.

Kushner denied colluding with Russian officials, but he disclosed one contact with a possible Russian hacker threatening to blackmail Trump over his unreleased tax returns.

"There was one more possible contact that I will note," Kushner said. "On October 30, 2016, I received a random email from the screenname 'Guccifer400.' This email, which I interpreted as a hoax, was an extortion attempt and threatened to reveal candidate Trump's tax returns and demanded that we send him 52 bitcoins in exchange for not publishing that information."

Kushner said he brought the email to the attention of a U.S. Secret Service agent, who told him to ignore the message and not reply, and he said he never heard from the sender again.

"To the best of my recollection, these were the full extent of contacts I had during the campaign with persons who were or appeared to potentially be representatives of the Russian government," Kushner said.

Trump has claimed he cannot release his taxes because they're under audit, although the Internal Revenue Service has said that does not matter.