The US is threatening a sweeping sanctions campaign against Iran's trading partners, and China is openly daring Washington to try — bad news for US leverage, and a warning sign for gas and diesel prices.

• China buys 90% of Iran's oil and says it will ignore what it calls illegal sanctions.
• Scott Bessent promised an "economic D-Day" against Iran but gave no details on what it would actually be.
• Hitting Chinese banks would wreck trade talks weeks before Xi visits Washington, and could shake the global financial system.
• China spent years building its own payment network, CIPS, after a Chinese bank was sanctioned over Iran in 2012 — it now has a tested workaround to the dollar.
• Sanctions on Russia are the cautionary tale: four years on, its economy and weapons output are both up.

Outlook: The bigger risk is oil — China cut its buying to hold prices down, and if it goes back to normal purchases, US gas and diesel prices could jump sharply.