The crews of some ships transiting the Strait of Hormuz have the right to refuse working on the vessels as they pass through the waterway — the world’s most important energy chokepoint — due to the recent danger associated with operating in the region.

The change is part of a temporary agreement by the so-called Warlike Operations Area Committee, which held an extraordinary meeting earlier this week and designated the strait as a high-risk area, according to a statement from union Nautilus International, one of the committee’s members. The committee also includes the U.K. Chamber of Shipping and Britain’s National Union of Rail, Maritime and Transport Workers.

“Crew can request to leave the ship at a preceding port” before entering the strait, according to the statement dated Aug. 2. This and other clauses in the agreement can be enacted only if the operator ignores flag-state and industry advice, Nautilus International spokeswoman Helen Kelly said by email.

The agreement applies to all vessels listed on the U.K. Chamber of Shipping, which can include British ships or those flagged under another country, she said. It also applies to seafarers of any nationality aboard those ships.

The Strait of Hormuz, at the mouth of the Persian Gulf, is the key waterway for about a third of all of the world’s oil shipped on tankers. In recent months, the Gulf region has been marred by a spate of vessel attacks, tanker seizures and the shooting down of drones, amid heightened geopolitical tensions and U.S. sanctions on Iran’s oil exports. Tanker captains are increasingly wary about traveling through the strait.

British vessels in particular have been at risk, following the U.K.’s seizure of an Iranian tanker near Gibraltar. Last month, Iran impounded a British-flagged vessel, the Stena Impero, which remains in the Middle Eastern nation’s custody. British oil giant BP Plc is now avoiding sending U.K. ships and crews through the strait.

The Warlike Operations Area Committee reached its agreement following government advice to avoid the area without U.K. naval support, according to the statement from Nautilus International, which has members in Britain, the Netherlands and Switzerland. The clauses apply only if flag-state and industry guidance aren’t complied with, it said.

“That includes U.K.-flagged vessels that refuse a military accompanied transit and vessels that do not take account of relevant guidance from industry bodies” like BIMCO and the International Chamber of Shipping, it said.

Seafarers on vessels transiting through the area may also receive double basic pay due to the risk involved, according to the statement. The strait’s temporary designation as a high-risk zone will be reviewed on Sept. 2 or earlier if advice from the British government changes, it said.