WASHINGTON — Congress has some questions for Felix Sater, a Russian-born former business associate of President Donald Trump who had previously been imprisoned for assault and has cooperated with federal investigators against the mafia in another case.

But lawmakers will have to wait a while longer to question Sater because he failed to show Friday for a scheduled interview with the House Intelligence Committee. The committee now plans to subpoena him.

Sater was scheduled to testify behind closed doors about his role in negotiations for a proposed Trump Tower in Moscow, which he boasted could help propel Trump to the White House. Trump's former personal lawyer, Michael Cohen, has pleaded guilty to lying to Congress about negotiations for the project, as part of special counsel Robert Mueller's investigation into Russian interference in the 2016 election.

“The committee had scheduled a voluntary staff-level interview with Mr. Sater, but he did not show up this morning as agreed," said Patrick Boland, a committee spokesman. "As a result, the committee is issuing a subpoena to compel his testimony.”

Rep. Val Demings, D-Fla., said Friday that Sater "must come testify."

House Intelligence Chairman Adam Schiff, D-Calif., said the panel is trying to learn more about the project and how it might compromise U.S. policy toward Russia if Trump were to pursue it after leaving office.

“We would like to present a fuller account of Trump Tower Moscow because that remains such a potentially compromising circumstance, if the president continues to want to make that deal, that our policy continues to be held hostage by the profit-making incentive there," Schiff told reporters Wednesday at the National Press Club.

Schiff said the project could remain a conflict of interest for Trump because he could pursue it after leaving office and such a large project would require the cooperation of Russian President Vladimir Putin.

“It may not be a crime to build a Trump Tower in Moscow or for Michael Cohen to seek the Kremlin’s help to do so," Schiff said this month at a hearing about Mueller's report. "But it is deeply compromising and not only because of the inducement of hundreds of millions of dollars."

Trump has maintained he is unfamiliar with Sater, despite Sater having an office on the same floor as Trump in his New York office building. In a videotaped deposition for a 2013 lawsuit, Trump said of Sater, “If he were sitting in the room right now, I really wouldn’t know what he looked like.” In a December 2015 interview with The Associated Press, Trump said, “I’m not that familiar with him.”

The committee had scheduled a public hearing in March with Sater, but then postponed it to await the imminent release of the Mueller report.

Sater had a colorful background before he became involved in the Trump Tower project. He was jailed for 15 months after his conviction for stabbing a man in the face with a broken margarita glass at the Rio Grande restaurant in New York in 1991. Sater also pleaded guilty to racketeering in 1998 in a $40 million stock-fraud scheme and cooperated with authorities against mafia defendants. Sater was later fined $25,000 with no prison time.

But Sater’s court records are largely sealed because of his longstanding cooperation with the FBI and other law enforcement agencies. Sater provided “information crucial to national security and the conviction of over 20 individuals, including those responsible for committing massive financial fraud and members of La Cosa Nostra,” Loretta Lynch, a former top federal prosecutor in New York, told Congress after she was nominated to be attorney general.

Salvatore Lauria, a co-defendant in the stock case, co-wrote a 2003 book that said he and Sater sought to reduce their sentences by acting as middlemen for the CIA to buy weapons that fell into the hands of mobsters after the fall of the Soviet Union. The scheme fell apart, according to the book The Scorpion and the Frog: High Crimes and High Times.

The Mueller report described Trump signing a letter-of-intent, which didn't require any payment, in November 2015 to pursue the Trump Tower project in Moscow that because of its size would require the support of Putin's administration. Cohen described Sater as a key go-between in Russian negotiations.

The goal, as Cohen described it, was to develop a Trump Tower in Moscow worth hundreds of millions of dollars because there was no certainty that Trump would win the election. Cohen said he briefed Trump and his children about the negotiations repeatedly. Sater promoted the deal to help Trump win the election.

“Buddy boy our boy can become president of the USA and we can engineer it,” Sater wrote in an email to Cohen on Nov. 3, 2015, the day after Trump signed the letter-of-intent. “You and I will get Donald and Vladimir on a stage together very shortly. That the game changer." Later the same day, Sater emailed: "We can own this election."

Sater repeatedly sought to get Trump and Cohen to visit Russia, to potentially meet Putin or Prime Minister Dmitry Medvedev, according to emails Mueller included in his charges against Cohen. But neither Trump nor Cohen visited during the campaign.

Trump said in written replies to Mueller's questions that the non-binding letter-of-intent required no expenditure and "was consistent with our ongoing efforts to expand into significant markets around the world." Trump said he had few conversations with Cohen about the project and they were not memorable.

"I do not recall being aware at the time of any communications between Mr. Cohen or Felix Sater and any Russian government official regarding the letter-of-intent," Trump said.

Cohen was sentenced to three years in prison after pleading guilty to charges including lying to Congress about the extent of talks about the project, which he said ended in January 2016 despite continuing to June 2016.

Cohen spent three full days in February testifying before the Senate and House intelligence committees, and the House Oversight and Reform Committee. He returned March 6 to Schiff’s panel.

More about President Donald Trump, Michael Cohen and Felix Sater:

Cohen takeaways: As Trump's former lawyer heads to prison, political and legal implications grow for White House

Michael Cohen, President Trump's former lawyer, ends 3 days of 'excruciating' testimony with another scheduled

Trump’s aides were eager to take Russian dirt on Clinton. But it wasn’t a conspiracy, Mueller report said