PARIS — French President Emmanuel Macron welcomed an announcement by Iran and the United States that the Strait of Hormuz is open, and at a Friday conference in Paris outlined plans for a strictly defensive international mission to secure shipping through the waterway. Representatives from about 50 nations and international organizations, including over 30 heads of state and government, joined the meeting.

In a post on X ahead of the gathering, Macron said the mission to provide security for shipping through the strait would be strictly defensive and limited to non-belligerent countries. "We all demand the full, immediate and unconditional reopening of the Strait of Hormuz by all parties," he said.

About a fifth of the world's oil usually passes through the Strait of Hormuz. Petroleum prices soared after the war started on Feb. 28 when Iran effectively shut the strait. Oil prices plunged after Iranian Foreign Minister Abbas Araghchi posted on X that passage for commercial vessels would remain completely open for the duration of a 10-day ceasefire in Lebanon.

U.K. Prime Minister Keir Starmer was greeted by Macron in the courtyard of the Élysée presidential palace on Friday afternoon. German Chancellor Friedrich Merz and Italian Premier Giorgia Meloni attended in person. Before the meeting, Starmer accused Iran of "holding the world's economy to ransom."

"The unconditional and immediate reopening of the strait is a global responsibility, and we need to act to get global energy and trade flowing freely again," Starmer said. Military planners will meet in London next week.

France and Britain have led military planning meetings for the initiative, echoing the coalition of the willing assembled to provide security for Ukraine. More than 40 nations have taken part in diplomatic or military meetings led by the two countries in recent weeks. The United States is not part of the planning for the Strait of Hormuz Maritime Freedom of Navigation Initiative.

An official said ensuring safe passage through the strait may require intelligence, mine-clearing capabilities, military escorts, and communication procedures with coastal states. Britain has discussed using mine-hunting drones deployed from the ship RFA Lyme Bay for a mission in the Strait of Hormuz. The Royal Navy has deployed the destroyer HMS Dragon to the eastern Mediterranean, and France has sent its nuclear-powered aircraft carrier, a helicopter carrier, and several frigates to the region.

Sidharth Kaushal, Research Fellow in Sea Power at the Royal United Services Institute, said mine-clearing and creating a warning system for maritime threats are more likely roles for the coalition than warships escorting commercial tankers.