The meeting at the Permanent Joint Headquarters in northwest London is intended to advance operational planning for reopening the strategic waterway when conditions permit, following what officials described as progress at international discussions held in Paris last week.

“The task today and tomorrow is to translate diplomatic consensus into a joint plan to safeguard freedom of navigation in the Strait and support a lasting ceasefire,” Defense Minister John Healey said in a statement.

The London conference follows talks co-chaired in Paris by British Prime Minister Keir Starmer and French President Emmanuel Macron that brought together representatives from more than 40 countries to address security in the strait, a critical global shipping route.

British and French officials have emphasized that the proposed multinational force would be defensive in nature and deployed only after a durable peace agreement is reached in the region.The United States and Iran, the principal parties to the ongoing conflict, did not participate in the Paris discussions.

A two-week ceasefire between the two countries was due to expire at midnight GMT on Tuesday, but US President Donald Trump said shortly before the deadline that it would be extended to allow further negotiations.

Both Washington and Tehran have accused each other of violating the truce, while the United States has maintained a blockade of Iranian ports.Downing Street had earlier indicated that a military planning summit would take place this week without providing further details

Trump stated that the underground facility is being built as part of the broader development linked to the ballroom, though he did not disclose further details regarding its purpose, scale, or operational timeline. The comments mark the first public acknowledgment of such a project beneath the White House grounds.

The president provided no specifics on the nature of the complex, including whether it is intended for security, command, or logistical functions. The White House and the Department of Defense have not issued formal statements elaborating on the project.

Large-scale subterranean infrastructure associated with executive facilities in Washington has historically been tied to continuity-of-government planning and national security requirements, though no direct confirmation was provided in this case.

Trump said the project is “under construction” and “ahead of schedule,” suggesting an accelerated timeline for completion. It remains unclear when construction began or which military or civilian contractors are involved.

The ballroom project itself has not been extensively detailed in official disclosures, and its integration with a military-linked underground facility raises questions about the scope and coordination of the development.

Presidential infrastructure expansions in Washington are typically subject to stringent security protocols, often involving coordination between multiple federal agencies. Any underground complex beneath the White House would likely fall under classified planning frameworks, limiting public visibility into its design and function.

No cost estimates or congressional oversight details were immediately available.