Central Command (CENTCOM) -- which is responsible for American forces in the Middle East -- said more than 10,000 US troops, over a dozen warships, and dozens of aircraft are taking part in the mission.

"During the first 24 hours, no ships made it past the US blockade and six merchant vessels complied with direction from US forces to turn around to re-enter an Iranian port on the Gulf of Oman," CENTCOM said in a post on X.

"The blockade is being enforced impartially against vessels of all nations entering or departing Iranian ports and coastal areas, including all Iranian ports on the Arabian Gulf and Gulf of Oman," it added.

But despite CENTCOM's assertion that no vessels made it through the blockade, tracking information from maritime data provider Kpler showed at least two ships sailing from Iranian ports crossed the Strait of Hormuz on Monday.

Tehran's forces effectively closed the strait after the start of the US-Israeli air campaign against the Islamic republic on February 28, and the US on Sunday announced its own blockade after peace talks with Iran failed.