China is Iran’s most important economic partner, buying some 90% of its oil exports and providing a financial lifeline to the heavily sanctioned regime. But since the US and Israel began their war with Iran six months ago, Beijing has offered little visible support to Tehran beyond criticizing the attacks. In late August, Treasury Secretary Scott Bessent threatened economic punishment against any country doing business with Iran as Washington sought to further isolate the Islamic Republic and end the war. His threats put China’s relationship with Iran under fresh scrutiny — and raised the prospect of another clash between Washington and Beijing ahead of a Trump-Xi…