A bipartisan group of six senators on Sunday called for Donald Trump’s administration to “immediately reverse course” on a plan to purchase diesel from Russia as part of an effort to lower high fuel prices.

Trump shocked lawmakers when he announced on social media Friday that he struck a deal with Russian President Vladimir Putin in a phone call. He said Russia will immediately supply more than 300,000 tons of diesel to the American and global market, followed by an additional 500,000 tons in November and 1 million tons “immediately thereafter.” Russia will deliver an additional 3 million tons “within a short period of time” after that, he wrote.

Four Republican senators and two Democratic senators signed onto the statement released Sunday in protesting the deal. They said the administration failed to consult with Congress or submit any explanation to justify its decision as required by statute.