A top adviser to the president of Ukraine made a plea to the White House to restrict all trade as he said that oil tanker from around the world were continuing to transport millions of barrels of oil out of Russian ports.

In an interview from Kyiv overnight on Tuesday, an economic adviser to President Volodymyr Zelensky urged the chief executives of Western oil and gas companies to pledge to not handle oil from Russia.

Mr. Ustenko said that Russia was using the money to feed a military machine that was killing people. All Russian ports must be closed.

The port of Novorossiysk on the Black Sea is one of Russia's major oil terminals and is also a hub for a pipeline that carries oil from neighboring Kazakhstan. It can be difficult to determine the oil's origin.

The continued oil trade out of places like Novorossiysk, which is heavily reliant on oil and gas imports from Russia, highlights the loopholes that allow Russian producers to continue to export their oil.

Mr. Ustenko said that American companies werebetting that trade. He mentioned a tanker that left Novorossiysk on Friday carrying nearly 100,000 tons of crude and is currently en route to the Netherlands. The Mediterranean Voyager is carrying a crude oil blend, according to independent shipment data.

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At least five other Chevron-chartered tanker were included in the data gathered by Ukraine on ships that were contracted to load oil at Russian ports.

In a statement, the company said that the oil on the ship came from the country of Kazakhstan and that it was carried out in compliance with U.S. law.

Russian oil, gas and coal were banned by President Biden. The shipping of oil, Russian or otherwise, from Russian ports to destinations in other nations is allowed. Mr. Ustenko urged the White House to ban American companies from handling Russian oil and gas exports.

Biden administration officials have stressed that Washington's restrictions go much further than those of other nations, including major U.S. allies in Europe. Europe is dependent on Russian gas and could face energy shortages if it were to cut off all supply. Financial restrictions have been placed on Moscow.

A spokeswoman for the National Security Council said that the United States was able to put in place its fossil-fuel embargo because of its strong domestic energy infrastructure. She said that not all of our allies and partners are currently in a position to join us.

The Mediterranean Voyager, the tanker leased by Chevron, in Istanbul in 2020.
ImageThe Mediterranean Voyager, the tanker leased by Chevron, in Istanbul in 2020.
The Mediterranean Voyager, the tanker leased by Chevron, in Istanbul in 2020.Credit...Cengiz Tokgöz

Western oil and gas companies have recently said that they will stop operations in Russia, including abandoning joint ventures with state-owned producers. Some large carriers have said they will stop transporting Russian oil and gas.

Russian ports are expected to ship at least 1.5 million barrels of crude oil and other oil-based products a day in the coming weeks, a significant decline from the four to five million barrels of crude they typically handled before the invasion. The majority of Russia's exports are oil, gas and coal.

Mr. Ustenko said that Greek shipping companies owned many of the tankers that continued to transport oil from Russian ports. He called on the Greek government to ban those shipments, as well as the German government to stop paying Russia for gas, and to put the funds into an account to be paid once Russia sued for peace.

Simon Johnson, an economics professor at the M.I.T. Sloan School of Management and a former chief economist at the International Monetary Fund, said those shipments exposed a major weakness in the U.S. embargo by allowing Russians to take advantage of higher oil prices.

To stem that trade, Washington needed to impose full sanctions similar to those imposed on Iran.

Energy experts have warned that the blended oil from the Novorossiysk line could be a route for Russian producers to continue to get oil out to global markets with the product's origins obscured. Over the past two decades, it typically carried a blend of about 13 percent Russian oil. The Russian state has a 24 percent stake in the consortium that owns the pipeline.

The spirit of the U.S. import ban should make it difficult for American companies to trade in that oil, according to a senior fellow at the Atlantic Council.

The implications are the same if the oil was bought from Russian traders.

The United States has tried to lead by example, but has refrained from disrupting other countries' energy needs by banning U.S. companies from delivering Russian oil to them.

The turmoil in oil and gas markets has spurred calls for a more rapid transition to renewable energy. Mr. Ustenko said that the crisis could lead to more investment in green energy.

Companies that trade with Russia have been censured quickly. Royal Dutch Shell was forced to pledge not to make future purchases after buying a shipment of Russian oil at a heavy discount.

In a televised address in Ukraine on Tuesday, President Zelensky made an appeal to people worldwide to boycott Russian products.