The US re-imposed its blockade of Iran's shipping and ports on July 13 as a deal to halt the war between them broke down in an attempt to cut off oil sales, Tehran's primary source of hard currency.

A renewed U.S. naval blockade has largely halted Iranian crude exports while extreme diesel-market tightness suggests oil prices may still be underpricing the disruption.

Trade sources say Iranian crude offers to China have declined and prices have risen as Washington's blockade disrupts Tehran's oil shipments.