Iranian oil exports to Asia have so far stayed strong, but with South Korea halting liftings in July, other buyers may come under increasing pressure to cease.

South Korea has bowed to pressure from the US government and become the first major buyer to halt oil imports from Iran. Seoul had been an increasingly important customer for Iran and took record volumes in 2017.

The 361,000 b/d that South Korea imported from Iran over the course of 2017 was more than any country bar China and...