The action against Foreign Minister Jorge Arreaza is the latest and loudest sign that the United States has no interest in negotiating with Maduro, a leftist firebrand whom more than 50 countries no longer recognize as president.

"The United States will not stand by and watch as the illegitimate Maduro regime starves the Venezuelan people of their wealth, humanity and right to democracy," Treasury Secretary Steven Mnuchin said in a statement.

Under the sanctions, any US assets of Arreaza will be blocked and US citizens will be prohibited from any dealings with the top Venezuelan diplomat, including in property.

Arreaza is the latest Venezuelan official to be targeted as President Donald Trump's administration tries to install in power Juan Guaido, the opposition leader.

But while most previous sanctions announcements alleged corruption or rights abuses, the Treasury Department did not cite specific violations by Arreaza, instead saying he was taken to task for his role as foreign minister.

"Treasury will continue to target corrupt Maduro insiders, including those tasked with conducting diplomacy and carrying out justice on behalf of this illegitimate regime," Mnuchin said.

Still backed by Russia

Maduro has survived three months of mounting pressure led by the United States, including efforts to deprive him of Venezuela's financial lifeline of oil sales, and still enjoys critical backing from Russia and China.

Russia denounced what it called "brutal" US pressure on Venezuela.

"We exhort the United States to return to the realm of international law, end its politics of blackmail and stop provoking tensions in Venezuela from abroad," the foreign ministry said in a statement.

"Washington has repeatedly displayed a categoric refusal to adopt the method of negotiation to resolve the situation," it said.

Maduro was re-elected in a vote widely condemned for irregularities. He presides over a crumbling economy, with inflation forecast to hit a mind-boggling 10 million percent this year and millions of Venezuelans having fled due to shortages of basic goods.

Arreaza, a former journalist who studied at Cambridge, has traveled several times to New York to represent Venezuela at the United Nations since the United States and most Latin American countries in January declared Maduro to be illegitimate.

Arreaza linked the sanctions against him to his call at the United Nations the previous day against the US "criminal blockade" of Venezuela, saying the reaction he heard had shown him "that we walk the right path."

"Today, the Trump administration responds with desperation against us. TRUTH hurts!" he tweeted.

Also targeted in the latest US sanctions was a Venezuelan judge, Carol Bealexis Padilla de Arretureta.

Standoff at embassy

At the United Nations, Arreaza had also warned of retaliation if the United States moves to expel leftist activists who are squatting as a protest in Venezuela's embassy in Washington.

The final Maduro envoys at the embassy left after the Organization of American States voted on April 10 to accept Guaido's envoy to represent Venezuela at the Washington-based body.

But activists have prevented Guaido's team from taking over the four-story embassy in the tony Georgetown neighborhood, accusing President Donald Trump of mounting a coup against a government that remains seated by the United Nations.

Trump has further alarmed activists by refusing to rule out military force in Venezuela, repeatedly saying that "all options" are on the table.

Elliott Abrams, the US envoy heading the push to topple Maduro, said Thursday that Guaido's ambassador would talk to security about expelling the activists, although he did not set a deadline.

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