The U.S. has asked tankers travelling through the Strait of Hormuz to sail only at specific times to guarantee military protection after Iran stepped up attacks on ships travelling at night, the Financial Times reported on Saturday.
Washington has been offering air-based defence since May to ships wanting to sail via a route hugging the Omani coast on the strait's southern side.
That period during which ships would be protected was cut down to two specific time slots daily around the start of September, the FT reported, citing emails sent by the U.S. naval co-ordination centre to maritime advisers.