Iran's Rouhani seeks closer UK ties with Johnson

In the letter published Sunday on Rouhani's website, the Iranian president congratulated Johnson on becoming prime minister Wednesday.

Rouhani said he hoped Johnson's "only one visit to Tehran" while serving as U.K. foreign secretary in 2017 and now his tenure as prime minister lead to a "further deepening of bilateral and multilateral relations."

Johnson took office on Wednesday amid a spike in tensions in the Persian Gulf and a diplomatic standoff between Britain and Iran. Iran seized a British-flagged tanker in the Strait of Hormuz this month after the British navy helped seize an Iranian supertanker loaded with crude oil near Gibraltar.