UK Foreign Secretary Jeremy Hunt spoke to his Iranian counterpart, Javad Zarif on Saturday to express disappointment with how the conflict between the two nations over the detention of tankers was developing.

The British official said on Twitter Iran was not acting to de-escalate the situation and said British shipping must be protected. This week, Iran detained a British-flagged tanker in what is perceived as retaliation for British seizure of a supertanker carrying Iranian oil in Gibraltar. Zarif tweeted, “unlike the piracy in the Strait of Gibraltar,” Iran’s move was meant to uphold international maritime law.