The U.S. has "neither supported nor enabled strikes by Ukraine outside of its territory," U.S. Secretary of State Antony Blinken said at press conference in Paris on April 2.
The Financial Times reported in March that the U.S. warned Ukraine to stop attacking Russian oil refineries, allegedly out of concern that strikes could raise global oil prices and increase the risk of further retaliation.
In an interview with the Washington Post on March 29, President Volodymyr Zelensky said that targeting Russian energy infrastructure is a legitimate military strategy.
The strikes serve as retaliation for Russian attacks on critical infrastructure and align with Ukraine's military objectives, Zelensky said.
Speaking at a joint press conference with French Foreign Minister Stephane Sejourne, Blinken said that the U.S. does "everything we possibly can to help Ukraine defend itself against this Russian aggression."
"At the same time, we have neither supported nor enabled strikes by Ukraine outside of its territory," Blinken said, responding to a question from a journalist about the Ukrainian strikes on Russian oil refineries.
Sejourne responded to the same question by saying that "this brings almost no comment on our behalf."
"The Ukrainian people are acting in self defense, and we consider that Russia is the aggressor," Sejourne continued.
"In such circumstances, there is hardly anything else to say. I think you understood me."
The comments from Blinken and Sejourne come as Ukraine carries out increasingly ambitious strikes on Russian oil refineries.
An attack on March 17 targeted a dozen Russian oil refineries, amounting to about 12% of Russia's oil-processing capacity, Bloomberg reported.
According to a Kyiv Independent source in the Security Service of Ukraine (SBU), Ukraine used a long-range drone to target one of Russia's largest oil refineries on April 2, located in the city of Nizhnekamsk in Tatarstan, over 1,000 kilometers (620 miles) from Ukraine's border.
The Ukrainian drone hit the refinery's primary oil processing facility, which has an annual production capacity of around 8 million tons, amounting to 2.6% of Russia's total annual oil-processing capacity, the SBU source said.
"We continue to work systematically to ensure that Russia has fewer and fewer opportunities to finance the war of aggression against Ukraine," the source added.