The Rosneft logo is pictured on a safety helmet, April 27, 2018. (Photo: Agencies)

The United States imposed sanctions on a subsidiary of Russian state oil major Rosneft and its president on Tuesday for allegedly helping the Venezuelan government to evade sanctions.

The US Treasury Department announced the sanctions on Rosneft Trading SA, the Geneva-based trading unit of Rosneft, the world's largest listed oil company by output, as it targeted Russia over its alleged backing for Venezuela's efforts to skirt US sanctions.

Russian state news agency Tass quoted an anonymous senior US government official as saying that the US Treasury Department took the action against Rosneft Trading and its President Didier Casimiro for "brokering the sale of Venezuelan oil globally on behalf of the illegitimate Nicolas Maduro regime".

The official also said the Russian company "actively attempted to evade US sanctions and provided an overwhelming amount of financial resources and hard currency".

Tuesday's sanctions came less than two weeks after the US slapped sanctions on state-owned Venezuelan airline Conviasa.

The senior official pointed out that the US was "somewhere in 50 to 60 percent of our maximum pressure strategy and campaign toward Venezuela", saying that it would continue to squeeze the Venezuelan government.

"The president has made clear over and over again that all options are on the table. We will continue to analyze all options," the official said.

Shares in Rosneft fell 2.7 percent, with the sanctions announcement coming near the close of trading on the Russian market, Reuters reported.

Rosneft Press Secretary Mikhail Leontyev called the sanctions "arbitrary" and said the company has never been engaged in illegal activities.

"We are acting strictly within the framework of international law. We have never breached even conditions of sanctions, as the US regulator repeatedly said. No evidence backs this decision. This is absolutely arbitrary," he said.

Assets to be frozen

Under the latest sanctions, the assets of Rosneft Trading and Casimiro in the US will be frozen.

The US will provide 90 days for countries and companies to complete their transactions with Rosneft Trading.

"I think this is a very significant step, and I think you will see companies all over the world in the oil sector now move away from dealing with Rosneft Trading," said Elliott Abrams, the US special representative for Venezuela.

Venezuela's state-owned oil and gas company PDVSA responded by condemning US sanctions.

"The US policy of unilateral sanctions is aimed at competitors on the global market, so that they can influence prices, control or eliminate main players, thus gaining hegemonic control over the global oil market," it said in a statement.