In a major escalation of trade tensions between Washington and Beijing, China's Ministry of Commerce (MOFCOM) has formally invoked its 2021 Blocking Rules for the first time to counteract U.S. sanctions against five Chinese oil refineries. Beijing has issued a prohibition order instructing all entities operating in China to disregard and not implement U.S. sanctions placed on five targeted refiners. The order comes weeks before a planned meeting between U.S. President Donald Trump and Xi Jinping. The U.S. Treasury has already sanctioned Chinese…