The Treasury Department also announced sanctions against three employees of the Internet Research Agency, a troll farm based in Russia that spread disinformation on social media as part of the Kremlin’s election interference campaign in 2016.
While Mr. Mnuchin has been steadfast in his loyalty to President Trump, the sanctions in some ways put them at odds on an issue of great significance to the president.
Mr. Trump has pushed unsubstantiated claims that Mr. Biden used his position as vice president to pressure the Ukrainian government to protect his son, who served on the board of a gas company owned by an oligarch who was widely seen as corrupt. A campaign waged by Mr. Trump and his personal lawyer Rudolph W. Giuliani to pressure the Ukrainian government to investigate the matter led to the president’s impeachment last year by the House of Representatives.
But Mr. Trump has continued calling attention to the issue, including promoting some of the material released by Mr. Derkach as recently as last month. Mr. Giuliani met with Mr. Derkach in December in Kyiv during a trip intended to collect damaging information about the Bidens, first reported by The New York Times.
Mr. Giuliani said in an interview Thursday night that he “felt comfortable” meeting with Mr. Derkach “because there were no sanctions against him” at the time. While he acknowledged that he “didn’t do much investigation” of Mr. Derkach, Mr. Giuliani said: “I have no reason to believe he is a Russian agent. There is nothing I saw that said he was a Russian agent. There is nothing he gave me that seemed to come from Russia at all.” But he added, “How the hell would I know?”
Mr. Giuliani emphasized that he did not give Mr. Trump or the State Department any information that Mr. Derkach had provided.
The White House did not immediately respond to a request for comment.
The Office of the Director of National Intelligence warned last month that Russia was “using a range of measures” to primarily harm Mr. Biden, specifically noting Mr. Derkach’s release of audio recordings.
Representative Adam B. Schiff, Democrat of California and chairman of the House Intelligence Committee, praised the Treasury sanctions in a statement as “appropriate and welcome,” and chided Mr. Trump for promoting “the same false claims and smears.”
As a result of Thursday’s actions, Mr. Derkach and the other individuals will have any assets or properties they hold in the United States frozen.
The Justice Department also filed charges on Thursday against one of the Russians who was penalized by the Treasury Department. Artem Mikhaylovich Lifshits was charged with wire fraud conspiracy for using the stolen identities of citizens in the troll-farm scheme to meddle in American politics.