(Bloomberg) -- The Biden administration is preparing to impose sanctions against Russia over the poisoning and jailing of opposition leader Alexey Navalny, according to three congressional aides briefed on the plans.

The sanctions will be unveiled as early as Tuesday, the aides said, offering no specifics and describing the moves on condition of anonymity ahead of a formal announcement. The measures will involve the State, Treasury and Commerce Departments, according to one aide.

The measures, if carried out, would be the first ordered by President Joe Biden against Russia and would set the tone for relations with his Russian counterpart, Vladimir Putin. The White House had no immediate comment on Monday night.

Navalny returned to Russia in January after being treated in Germany for a nerve agent attack. He was detained shortly after landing at Moscow’s Sheremetyevo airport. Western governments and Navalny have accused the Kremlin of being behind the attempted assassination. Russia denies that and has said that Navalny’s imprisonment is an internal matter.

Last month, Biden called for Navalny’s release, saying he was “targeted for exposing corruption and should be released immediately and without condition.”

Since then, Navalny has been sentenced and begun serving a two-and-a-half-year term. Last week, he was moved to a notorious penal camp in the Vladimir region about 60 miles (100 kilometers) east of the Russian capital.

On Monday, European Union ambassadors approved sanctions against four senior Russian law enforcement officials over Navalny’s detention, according to three people familiar with the decision. The measures are expected to be formally adopted by the bloc’s 27 members later this week, said one of the people, who requested anonymity to discuss a private process.

During his first call with the Russian leader, in late January, Biden said he “made it clear to President Putin in a manner very different from my predecessor that the days the United States rolling over in the face of Russia’s aggressive actions, interfering with our elections, cyber attacks, poisoning citizens are over.”

Biden called the jailing of Navalny “politically motivated.” His administration also has Moscow in its sights for what U.S. intelligence agencies indicate was Russia’s likely role in the SolarWinds Corp. cyber attack.

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