Britain's foreign minister Yvette Cooper will meet with US Secretary of State Marco Rubio on Friday, after President Donald Trump renewed his criticism of London for ceding sovereignty of the Chagos Islands, which is home to a US-UK air base.
Last year British Prime Minister Keir Starmer agreed a deal to transfer sovereignty of the Indian Ocean islands to Mauritius, while keeping control of one - Diego Garcia - through a 99-year lease that preserved US operations at the base.
Washington last year gave its blessing to the agreement, but Trump has since changed his mind several times. In January, Trump described it as an act of "great stupidity," but earlier this month said he understood the deal was the best Starmer could make, before then renewing his criticism this week.
Cooper is meeting Rubio to discuss defense and security issues in Washington as Trump also toughens his rhetoric on Iran, saying Tehran must make a deal over its nuclear program in the next 10 to 15 days, or "really bad things" will happen.
The Diego Garcia base has recently been used for operations in the Middle East against Yemen's Houthis and in humanitarian aid to Gaza.
Trump claims Chagos accord big mistake
Although on Tuesday Rubio's State Department said it backed the Chagos accord, the next day Trump said Britain was making a big mistake.
"DO NOT GIVE AWAY DIEGO GARCIA!" Trump wrote in a post on Truth Social, saying the base could be called upon in any future military operation to "eradicate a potential attack" from Iran.
Under the conditions for using the joint base, Britain would need to agree in advance to any operations out of Diego Garcia.
On Thursday, Britain's The Times newspaper reported that Trump's latest criticism of the Chagos deal came because Britain was yet to give permission to use the bases for future strikes against Iran, owing to concerns they may breach international law.
Asked about The Times report, Britain's Ministry of Defense said on Thursday it does not comment on operational matters and that Britain supported the ongoing political process between the US and Iran.