One of Donald Trump’s former real estate partners has agreed to be interviewed by the Senate Judiciary Committee. Felix Sater, who tried to broker a deal to build a Trump Tower in Moscow during the 2016 election, told TPM that he will cooperate.

“I intend on cooperating fully with any and all government agencies and investigations,” Sater said in a text to TPM. “And if I am called I hope you make the trip to witness it in person because I don’t think it’s going to go the way of everyone’s favorite narrative.”

The request, from California Democrat Dianne Feinstein, asks for a number of specific documents that could shine a light on how Trump’s business interests in Russia intersect with his policymaking, and what role those interests might have played in the 2016 campaign.

“Mr. Sater intends to be fully cooperative with any and all government investigations in this matter,” Sater’s attorney Robert Wolf told TPM in an emailed statement. McClatchy first reported Sater’s cooperation Wednesday night.

Sater told TPM this summer that he has regularly worked for US intelligence since his arrest for fraud in a pump-and-dump stock scheme in 1998.

The California Democrat’s invitation is not a formal Judiciary Committee subpoena, but Sater’s cooperation could fill some significant gaps in the story of Donald Trump’s business dealings in Russia. Feinstein asked Sater to turn over “all documents related to the proposed Trump Tower in Moscow,” as well as a any communications with the campaign or related to the hacked emails from the Democratic National Committee and the Clinton campaign, and everything related to Sater’s financial dealings with the Trump Organization.

“In light of your involvement in brokering business deals for the Trump Organization in Russia, and your apparent efforts to leverage business relations to wield influence and curry favor with high-ranking Russian officials and candidate Trump,” Feinstein wrote, “we believe that you have information that would advance the Committee’s understanding of Russian interference in the 2016 election and the Committee would ask to schedule an interview with you to take place in November 2017.”

Feinstein also asked for documents related to the notorious Ukraine-Russia “peace deal” Sater tried to broker between Trump lawyer Michael Cohen and ousted Ukrainian politician Andrii Artemenko in January. At that meeting, Cohen said Sater had given him a written proposal in a sealed envelope, which Cohen said he gave to Michael Flynn. The document in that envelope has never been produced.