Beijing says it will take ‘all necessary measures’ to protect its interests as US steps up efforts to isolate TehranExplainer: could US sanctions threaten China-Iran ties?China has denounced the threat of US sanctions for its trade with Iran, saying any such measures would be illegal, and warned it would take “all necessary measures” to protect its national interests.Beijing’s rejection of the US threat of secondary sanctions for any country or entity continuing to trade with Tehran ha