Tighter US restrictions on Iranian oil exports have again raised concerns over the critical Strait of Hormuz passage. Despite Iranian rhetoric, a blocking move looks off the cards given that some buyers appear set to resist US pressure.

The US announcement that it will not be renewing waivers that permit some countries to continue importing limited volumes of Iranian oil has brought the Strait of Hormuz back into the spotlight (see map). Iran was quick to flag up the strategic chokepoint,...