Foreign ministers from almost three dozen countries will meet Thursday in an effort to exert diplomatic and political pressure to reopen the Strait of Hormuz, a vital shipping route that has been disrupted by the U.S.-Israeli war against Iran.

The U.S. is not among the countries attending Thursday’s meeting, which comes after President Donald Trump indicated that he believes securing the waterway is not primarily a U.S. responsibility. Trump has also criticized America’s European allies for not supporting the war and reiterated his position on potentially withdrawing the U.S. from NATO.

British Prime Minister Keir Starmer said the virtual meeting chaired by Foreign Secretary Yvette Cooper “will assess all viable diplomatic and political measures we can take to restore freedom of navigation, guarantee the safety of trapped ships and seafarers and to resume the movement of vital commodities.”

Iranian attacks on commercial ships, and the threat of more, have halted nearly all traffic in the waterway that connects the Persian Gulf to the rest of the globe’s oceans, shutting a critical path for the world’s flow of oil and sending petroleum prices soaring.

There have been 23 direct attacks on commercial vessels in the Gulf since the war began on Feb. 28 and 11 crew members have been killed, according to Lloyd’s List Intelligence, a shipping data firm.

Traffic through the strait has slowed significantly, with remaining tanker traffic largely consisting of sanctions-evading vessels carrying Iranian oil, Lloyd’s List Intelligence said in a briefing Thursday. It said a complex system under which Iran determines passage continues to operate as Tehran maintains control over the key waterway.

In a televised address on Wednesday night, Trump said countries that depend on oil flowing through the Strait of Hormuz “must grab it and cherish it” — because the U.S. would not.

No country appears willing to try to open the strait by force while fighting continues and Iran retains the capability to target vessels with anti-ship missiles, drones, attack craft and mines. But Starmer said Wednesday that military planners from an unspecified number of countries will meet soon to work on how to ensure security for shipping “after the fighting has stopped.”

In the meantime, 35 countries including the U.K., France, Germany, Italy, Canada, Japan and the United Arab Emirates have signed a statement calling on Iran to stop its attempts to block the strait and pledging to “contribute to appropriate efforts to ensure safe passage” through the waterway.

Thursday’s meeting is considered a first step, to be followed by “working-level meetings” of officials to develop further details.

Starmer said resuming shipping “will not be easy,” and will require “a united front of military strength and diplomatic activity” alongside partnership with the maritime industry.

The international effort has similarities to the “coalition of the willing” led by the U.K. and France to support Ukraine’s security after a future ceasefire in that war. The coalition is, in part, intended to demonstrate to the Trump administration that Europe is increasing its role in its own security.

The urgency of stronger continental defenses has been reinforced by Trump’s recent suggestion that the U.S. could leave NATO. He said Wednesday that the military alliance had “treated us very badly.”

David B. Roberts, reader in Middle East Security Studies at King’s College London, said international coalition-building efforts are “definitely linked to the wider Trumpian criticism toward NATO, that other members of NATO are not pulling their weight.

“Without a doubt, this is Britain and France, notably, trying to lead the way, to very visibly show a certain sort of utility” to the Trump administration.

“There’s also the very pragmatic reality that America is an oil exporter,” he added. “The immediate pressures about the fallout of the of the energy blockage in the Gulf, they fall on Europe and of course Asia, far more than America.”