Dozens of countries are attending a UK-led conference on Thursday to form a coalition to re-open the Strait of Hormuz.
Prime Minister Keir Starmer agreed with European Commission President Ursula von der Leyen, in a phone call on Wednesday, that efforts must be made to ensure Iran does not hold the international economy hostage through its closure of the waterway.
“They condemned Iran’s appalling action in the Strait of Hormuz, which is holding the global economy hostage,” a statement from Downing Street said. “They agreed allies must come together and work on a viable plan for full freedom of navigation to resume when circumstances allow.”
Mr Starmer also spoke to Nato Secretary General Mark Rutte about the importance of the trade route, through which a fifth of the world's oil output normally transits every day.
“It was vital that freedom of navigation was restored in the Strait of Hormuz … the leaders agreed,” a separate statement said.
UK Foreign Secretary Yvette Cooper is set to host the coalition talks. The British diplomatic initiative is understood to include more than 40 countries, such as France, Germany, some Gulf nations, plus ship registry locations, to restore access to the strait.
In an opening address, Ms Cooper condemned “Iranian recklessness” for “hitting global economic security”. She called for "action to guarantee the safety of trapped ships and seafarers, and [the] effective co-ordination that we need across the world to enable a safe and sustained opening of the strait".
A total of 35 countries signed a declaration on March 19 that condemned the “de facto closure of the Strait of Hormuz by Iranian forces”.
Next week, military planners will consider how to make the strait “accessible and safe” after the fighting has stopped, UK officials said. This is not expected to a role for Royal Navy warships in policing the waterway.
In an address from the White House on Wednesday, President Donald Trump made clear his frustration with Europe, as a major beneficiary of Hormuz traffic that has refused to take part in the war against Iran. The US leader is furious the countries of Nato have not backed his war and has refused to rule out quitting the alliance.
“The countries of the world that do receive oil through the Hormuz strait must take care of that passage,” he said. “They must cherish it. They must grab it and cherish it. They can do it easily.
“We will be helpful, but they should take the lead in protecting the oil that they so desperately depend on.
“So, to those countries that can’t get fuel, many of which refused to get involved in the decapitation of Iran, we had to do it ourselves.”
Cathy Ashton, the former EU foreign affairs commissioner who negotiated a now defunct nuclear deal with Iran, described Ms Cooper's summit as a "fishing mission". She said it was unlikely to be a conversation about firm steps to take military action to open up the strait.
“It will not be focused on ‘lets put the navy together, let’s go off and do something on a military basis directly'," she told a panel hosted by the European Leadership Network. "That doesn’t mean there won’t be conversations about military action.”
