He's the key figure in a plan pursued during Donald Trump's 2016 campaign to build a Trump Tower in Moscow.
And on Tuesday real estate developer Felix Sater appeared on Capitol Hill to tell the House Intelligence Committee what he knows about the now-abandoned project.
Sater was due to appear behind closed doors last month but failed to show, saying he was sick.
Sater worked with former Trump lawyer Michael Cohen and Russian contacts on the plan to build the tower.
He came under scrutiny after Cohen, now serving 3 years in prison, pleaded guilty to lying to Congress about when the Tower talks had ended.
(SOUNDBITE) (English) MICHAEL COHEN, FORMER TRUMP LAWYER, SAYING: "I am ashamed of my weakness and misplaced loyalty." Cohen had told lawmakers it was January 2016 but later admitted the talks went on until well after Trump had clinched the nomination... and while he was praising Vladimir Putin on the trail.
(SOUNDBITE) (English) DONALD TRUMP, THEN REPUBLICAN PRESIDENTIAL CANDIDATE, SAYING: "When people like me, I like them.
Even Putin, you know Putin.
They want me to disavow Putin, Putin of Russia said Trump is a genius, he'll be the next leader.'" Sater has said he and Cohen talked about giving the Tower's $50 million penthouse to Putin as a marketing stunt.
Sater is the latest but likely far from the last to be interviewed by House lawmakers in a range of Russia-related probes.
The House Judiciary Committee said Tuesday it would seek subpoenas to speak with, among others, Trump senior adviser and son-in-law Jared Kushner, former national security adviser Michael Flynn, former White House Chief of Staff John Kelly, and former Attorney General Jeff Sessions.
Meanwhile, Reuters has learned Justice Department lawyers last month interviewed former British spy Christopher Steele.
He's the author of a controversial dossier that detailed allegations that Trump's campaign colluded with Moscow and made salacious claims about Trump himself, which he denies.
(SOUNDBITE) (English) U.S. PRESIDENT DONALD TRUMP SAYING: "A fake and phony dossier - did you hear about the dossier?" Steele's interview is part of the agency's probe into the origins of the FBI investigation into Trump.
Information in the dossier helped prompt the FBI to seek a special warrant to monitor former Trump adviser Carter Page.
Special Counsel Robert Mueller ultimately found insufficient evidence of a criminal conspiracy between Trump's campaign and Russia, but he failed to clear Trump of trying to impede the probe, leaving further action to Congress.