U.S. Senate investigators are demanding President Donald Trump’s longtime political supporter Roger Stone produce documents related to a meeting he had with a Russian citizen offering dirt on Hillary Clinton during the 2016 presidential campaign.

“I have no reason to dissemble or hide it because nothing illegal or improper happened at the meeting or subsequent to the meeting,” Stone told ABC News during an interview this week.

The committee’s request comes days after it was revealed that in May 2016 Stone was approached through intermediaries by Henry Greenberg, reportedly a Russian citizen who claimed to have damaging material on Hillary Clinton, as first reported by The Washington Post on Sunday.

Over lunch in Sunny Isles, Florida, a community north of Miami that is popular with Russian transplants and tourists, Greenberg reportedly offered to sell Stone damaging material on Clinton for $2 million – a deal Stone said he declined.

Stone served as an early adviser to Trump’s presidential campaign but left amid controversy in 2015. He told ABC News he “never discussed the matter with Donald Trump or anyone in his campaign” and he “flatly rejected this proposal as ludicrous and frankly forgot about it.”

Stone now alleges he was set up by the FBI because he believes Greenberg worked as an FBI informant.

There is no outside evidence to support the claim that Greenberg was working as an FBI informant at the time he approached Stone.

Calls by ABC News to phone numbers associated with Greenberg were not immediately answered. Greenberg told The Post he had worked with the FBI but that ended in 2013.

The new disclosure raised concerns among Democrats overseeing congressional investigations into allegations of Russian collusion in the 2016 presidential campaign because Stone had never mentioned the contact when he testified before the House Intelligence Committee last year.

“In multiple respects now, the testimony of Roger Stone appears inaccurate or deliberately misleading,” Rep. Adam Schiff, D-Calif., the ranking Democrat on the House Intelligence Committee, said Sunday, referring to Stone’s September 2017 committee testimony.

Stone was asked about foreign contacts during his interview in September 2017.

"I just didn't remember,” he told ABC News on Wednesday, noting that 2016 “was a pretty busy year. I don't think a failure of memory constitutes a perjury."

Attorneys for both men sent letters dated June 15 to House Intelligence Committee Chairman Devin Nunes, R-Calif., seeking to revise their respective prior testimony to the committee to include reference to the interactions with Greenberg. Both letters say the men forgot about the interactions, but have since had their memories refreshed.