Washington has also circulated a proposal, seen by Reuters, to partners for a new multinational maritime coalition, the Maritime Freedom Construct (MFC), aimed at establishing a post-conflict security architecture for the Middle East and reopening the strait once conditions stabilise.

The MFC would work with a separate Franco-British maritime mission involving around 30 countries that seeks to lay the groundwork for safe transit through the strait once the situation stabilises or the conflict is resolved, with Iranian coordination.

Some states have signalled any mission would require a UN mandate before committing military assets.

“The MFC is complementary to other maritime security task forces, including the maritime planning effort the UK and France are leading,” according to an informal diplomatic document sent to governments and seen by Reuters.

“The MFC will remain structurally independent, though close coordination is essential to achieve the strongest maritime security architecture possible.”

(Reporting by John Irish; additional reporting by David Brunnstrom in Washington; Editing by William Maclean and Deepa Babington)