WASHINGTON — House Democrats have summoned Steven Mnuchin, the Treasury secretary, to Congress on Thursday to deliver a classified briefing about the Trump administration’s plans to end sanctions on companies linked to the billionaire Russian oligarch Oleg V. Deripaska.

The briefing is an early instance of Democratic lawmakers flexing their new oversight muscles after taking control of the House last week. Such requests from Democrats were generally ignored or rebuffed during President Trump’s first two years in office, but cabinet officials are expected to face intense scrutiny over past decisions.

Congress is reviewing the administration’s decision — announced in December by the Treasury Department — to lift sanctions against three companies that Mr. Deripaska controls, EN+, Rusal and JSC EuroSibEnergo. Rusal is the world’s second largest aluminum company and concerns about its fate roiled the industry after the Trump administration announced sanctions last year.

The Treasury Department delayed the implementation of the sanctions several times amid an aggressive lobbying campaign by Mr. Deripaska’s corporate empire. The administration ultimately decided to lift the sanctions in the waning days of the last Congress — timing seen as intended to reduce the likelihood that Congress might block the move.