Iran's grip on the Strait of Hormuz has jolted the world economy, causing a spike in fuel prices that has rippled through other sectors with effects far beyond the Middle East.

It has also left tens of thousands of mariners and hundreds of ships stranded in the Persian Gulf.

Iran effectively seized control of the critical waterway after the US and Israel attacked it on February 28. Weeks of heavy bombing and a US naval blockade imposed last month have yet to loosen its grip. Iran says it will only reopen the strait if the war ends and the blockade is lifted. US President Donald Trump is seeking wider concessions, including the rollback of Iran's disputed nuclear programme.