Steven Mnuchin, U.S. Treasury secretary, speaks during a Financial Stability Oversight Council (FSOC) meeting at the U.S. Treasury in Washington, D.C.

Treasury Secretary Steven Mnuchin will brief lawmakers in the House of Representatives on Thursday about his department's plan to terminate sanctions on three companies linked to Oleg Deripaska, a Russian billionaire with ties to Russian President Vladimir Putin.

The meeting will take place behind closed doors, according to a senior Democratic aide. It is scheduled exactly one week after Democrats officially took the majority in the House and is among the first instances of the party using its newfound power to conduct oversight of the Trump administration.

The meeting follows Treasury's Dec. 19 notification to Congress that it would end sanctions on Rusal, EN+ and EuroSibEnergy in 30 days. Mnuchin said at the time that the decision was made after the companies "committed to significantly diminish Deripaska's ownership and sever his control."

Deripaska, a metals tycoon and close friend and ally of Putin, remains sanctioned, meaning no American may conduct business dealings with him directly or indirectly. He has come under scrutiny in the United States for his ties to the Kremlin as well as to Paul Manafort, who served as President Donald Trump's campaign chairman and has since been convicted of a range of federal crimes in connection with special counsel Robert Mueller's Russia probe.

Manafort, working with Konstantin Kilimnik, a business partner with suspected ties to Russian intelligence, reportedly offered to provide Deripaska with personal briefings on the status of the Trump campaign in 2016. Mueller has accused Manafort of sharing 2016 polling data with Kilimnik, Manafort's attorneys inadvertently revealed this week.

In its notification to Congress, Treasury said that Deripaska's interests in the three companies were "effectively frozen."

"Deripaska cannot obtain cash either in return for his shares or from future dividends issued by En+, Rusal, or ESE," Treasury said.

But on Tuesday, the chairs of seven House committees wrote a letter to Mnuchin noting that the terms of the agreement appeared to keep intact Deripaska's significant ownership of one of the companies, EN+, while "reportedly transferring some shares and financial interests to the Kremlin-linked sanctioned Russian bank VTB."

The Democrats said they had a number of additional questions to ask Mnuchin before they can fully assess the plan. They gave him until Friday to provide the briefing.

Deripaska was sanctioned alongside a slate of Russian oligarchs, businesses and government officials in April for election interference and other reasons. At the time, Treasury said that Deripaska had been accused of unlawfully wiretapping a government official, taking part in extortion and racketeering, ordering the murder of a businessman, and being tied to Russian organized crime.