The US military has reduced the daily window in which it offers air defense to commercial ships transiting the Strait of Hormuz, the Financial Times (FT) reports on Saturday.
Since May, Washington has sought to break Iran's control of Hormuz by providing air defense for vessels sailing through the strategic strait along a southern route hugging the coast of Oman.
Iran imposed a blockade on the strait shortly after the US and Israel launched an unprovoked war on the Islamic Republic on February 28.
However, the US began limiting the time slots in which vessels can receive protection from US aircraft as of the start of this month, FT reported.
The move comes in response to stepped-up Iranian attacks on ships transiting Hormuz, particularly at night. Ships are reportedly advised but not required to sail during the air defense time slots.
To receive protection, shipowners must apply to a US naval coordination center known as the Naval Cooperation and Guidance for Shipping (NCAGS).
Upon approval, the vessels received coordinates to follow during a broad time window. However, that window was "reduced to two specific time slots daily around the start of September," FT wrote, citing emails NCAGS sent to maritime advisors.
Vessels are now being told to begin their journey at specified times, such as 9:00 am, to receive air defense.
"We are now providing recommended transit times that vary by day. Your vessel is not required to go during these times, but it is encouraged to receive the best support," one NCAGS email said.
"Transiting during a period of darkness has not proven to be the most secure time of day," stated another email, highlighting the increased threat of Iranian attacks at night.
Iranian forces have attacked dozens of vessels attempting to pass through the strait since the beginning of the war, greatly limiting the oil exports of Washington's Gulf allies.
The US responded by imposing a naval blockade on Iranian ports in a bid to block Tehran's own oil exports. Before the war, at least 20 percent of world oil exports passed through Hormuz.
Not only security but also cost considerations may have influenced the US decision to reduce the protected transit window.
Joshua Tallis, a researcher at the Center for Naval Analyses (CNA), stated that it costs the US Navy $25,000 to $75,000 an hour to operate its advanced aircraft.
Both Iran and the US stepped up their attacks on commercial vessels in the region earlier this week. Iran targeted two vessels and eight oil tankers in Hormuz in response to US strikes on five Iranian tankers. The US launched the strikes following an attack by Iran's Islamic Revolutionary Guard Corps (IRGC) on a US warship days earlier.
"These waters aren't safe," stated Michelle Wiese Bockmann, an analyst at maritime intelligence firm Windward. Bockmann estimated that oil exports from Gulf countries other than Iran in August stood at about two-thirds of prewar levels, largely because of exports rerouted through pipelines to bypass Hormuz.
Meanwhile, Iranian Foreign Ministry spokesman Esmail Baghaei announced on Saturday that foreign ministers from several Gulf states will meet in Oman on Monday to exchange views on regional issues, including talks between Iran and Oman on designating safe routes for transiting the strait.
Baghaei added he hoped the meeting would improve understanding among regional countries and contribute to joint regional security.