Felix Sater, a Russian-born businessman and longtime associate of President Donald Trump, was interviewed by the Senate Intelligence Committee on Wednesday.

Sater was a key participant in two events that are critical to the ongoing Russia investigation: the Trump Organization's efforts to build a Trump Tower in Moscow during the US election, and Trump officials' push for a controversial Russia-friendly "peace plan."

Trump's longtime personal lawyer, Michael Cohen, was also instrumental in both events, and Sater's testimony could help investigators connect the dots and gauge whether other, higher-ranking members of the Trump Organization or Trump administration played a role.

Felix Sater, the Russian-born businessman linked to President Donald Trump, has been interviewed by the Senate Intelligence Committee as part of its Russia investigation, BuzzFeed News reported.

The interview took place Wednesday and likely centered around two pivotal events in which Sater was a participant: the Trump Organization's effort to secure a Trump Tower deal in Moscow at the height of the 2016 US election, and Trump transition officials' proposal for a controversial Ukraine-Russia "peace plan" that appeared to favor Moscow.

"Mr. Sater has long served as a high-level intelligence asset for various government agencies. He is a real estate developer, an entrepreneur who continues to be a proud American," said Ronn Torossian, a spokesperson for Sater.

According to BuzzFeed, Senate investigators recently asked the US Treasury Department for financial information related to Sater and his real-estate company, Bayrock Group, which did business with the Trump Organization in the early 2000s and currently has its offices at Trump Tower in New York.

Sources told BuzzFeed that while it's unclear whether the Treasury's Financial Crimes Enforcement Network (FinCen) gave lawmakers documents related to Sater, it has identified 23 instances of suspicious activity connected to his financial transactions.

In addition to Sater, Trump's longtime personal lawyer Michael Cohen was also instrumental in both events, and Sater's testimony will likely help investigators get a clearer picture of the episodes and whether other higher-ranking members of the Trump administration or Trump Organization played a role.

Trump Tower Moscow

Sater was in touch with Cohen about the Trump Tower deal in October and November 2015, when Trump was a Republican presidential candidate.

Sater first sent a letter of intent to Cohen outlining the terms of the "Trump World Tower Moscow" deal on October 13, 2015, The New York Times reported. Andrey Rozov, a Russian investor, had already signed it by the time Sater forwarded it to Cohen for Trump's signature.

"Lets make this happen and build a Trump Moscow," Sater wrote in a note attached to the letter. "And possibly fix relations between the countries by showing everyone that commerce & business are much better and more practical than politics. That should be Putins message as well, and we will help him agree on that message. Help world peace and make a lot of money, I would say that's a great lifetime goal for us to go after."

Weeks later, the two men exchanged a series of emails gearing up to celebrate the Trump Tower Moscow deal. In the emails, obtained by The Times, Sater bragged about his relationship with Russian President Vladimir Putin and told Cohen he would "get all of Putins team to buy in" on the deal.

"Our boy can become president of the USA and we can engineer it," Sater wrote, according to The Times.

Sater added: "I will get Putin on this program and we will get Donald elected."

U.S. President Donald Trump and Russia's President Vladimir Putin talk during the family photo session at the APEC Summit in Danang, Vietnam November 11, 2017. Reuters/Jorge Silva

Sater later walked back his comments in an interview with BuzzFeed, telling the outlet he had exaggerated his relationship with Putin in order to secure the deal.

He also told Talking Points Memo last August that his "last Moscow deal" for the Trump Organization "was in October of 2015" but that it did not end up going through.

"Once the campaign was really going-going, it was obvious there were going to be no deals internationally," Sater said. "We were still working on it, doing something with it, November-December."

But Cohen was advocating the project as late as January 2016, when he contacted Dmitry Peskov, a top aide to Putin, and asked for his help in pushing the Trump Tower Moscow deal through.

Sater, meanwhile, added a whole new dimension to the story when he told MSNBC last month that the Trump Organization was actively negotiating with VTB Bank, a sanctioned Russian bank, during the election to secure financing for the building.

"I had a local developer there [in Russia], and I had the Trump Organization here [in the US], and I was in the middle," Sater told host Chris Hayes. "And the local developer there would have gotten financing from VTB and/or another Russian bank, but VTB at that point was the go-to bank for real-estate development."

Sater's revelation to Hayes was likely a key component of lawmakers' questions on Wednesday.

Ukraine-Russia 'peace plan'

Sater and Cohen were also instrumental in pushing for a controversial Ukraine-Russia "peace plan" after Trump was elected president.

The Times reported that Cohen, Sater, and the Ukrainian politician Andrey Artemenko were the key figures involved in pushing for the proposal, which was delivered to then national security adviser Michael Flynn last year. While Cohen and Sater are both longtime associates of Trump, Artemenko is said to have met with the Trump campaign before the election and has signaled opposition to Ukrainian President Petro Poroshenko.

Poroshenko, who assumed the presidency in 2014 after the ouster of Viktor Yanukovych, has demonstrated more affinity than his predecessor toward the West.

The plan Artemenko, Sater, and Cohen pushed would have the US lift sanctions on Russia in exchange for Moscow's withdrawing its support for pro-Russia separatists in eastern Ukraine. It would also allow Russia to maintain control over the territory of Crimea, which it annexed in 2014.

Michael Cohen, President Donald Trump's personal attorney, looks on as his attorney (not pictured) delivers a statement to reporters after meeting with Senate Intelligence Committee staff on Capitol Hill in Washington, U.S., September 19, 2017. Aaron P. Bernstein/Reuters

Cohen attracted significant scrutiny when he offered evolving explanations of his involvement in the conception and delivery of the plan.

"Mr. Cohen told The Times in no uncertain terms that he delivered the Ukraine proposal to Michael Flynn's office at the White House," The Times' deputy managing editor said in a statement after the newspaper published the story. "Mr. Sater told the Times that Mr. Cohen had told him the same thing."

Cohen confirmed some details of the Times story to The Post, saying he met with Sater and Artemenko at a hotel in Manhattan in late January 2017 to discuss the plan. He added that the meeting lasted less than 15 minutes and that he left with the plan in hand.

He told Business Insider in February 2017 that he did not know what the plan was. Cohen then shifted his story again, saying he met with Artemenko for less than 10 minutes in New York to discuss a proposal Artemenko said "was acknowledged by Russian authorities that would create world peace."

"My response was, 'Who doesn't want world peace?'" Cohen said.

Later, Cohen told NBC News that even if he had delivered the peace plan to the White House, it wouldn't be a big deal.

"So what?" Cohen said. "What's wrong with that?"