US Republican Senator Thom Tillis questioned the legality of President Donald Trump's decision to temporarily relax sanctions on Russian diesel, stating in a Sunday interview that the sanctions relief could violate congressional law. Tillis argued that Trump is not following the law, and warned that his support for Trump's legislative priorities would be contingent on the White House reversing course. Trump's decision, which aims to bring down record-high fuel prices, has unsettled some Republican lawmakers who continue to support Ukraine. Separately, Tillis joined a bipartisan group of senators in issuing a letter to denounce the sanctions relief for Russia, stating that the US should not provide Russia with a financial lifeline. US Treasury Secretary Scott Bessent defended the administration's decision, asserting it was necessary to alleviate surging diesel prices and was made with all legal authorities.