US military reports no ships have breached Iranian blockade

More than 10,000 US military personnel, more than a dozen warships and dozens of aircraft were enforcing the blockade, it said.

"The blockade is being enforced impartially against vessels of all nations entering or departing Iranian ports and coastal areas," the statement added.

In a note sent to seafarers about the blockade on Monday, the US military said: "Any vessel entering or departing the blockaded area without authorisation is subject to interception, diversion, and capture."

The Monday note said the blockade would include all of Iran's coastline, but humanitarian shipments including food, medical supplies and other essential goods would be permitted, subject to inspection.