UK Prime Minister <a href="https://www.thenationalnews.com/tags/keir-starmer/" target="_blank">Keir Starmer</a>’s national security adviser is to travel to <a href="https://www.thenationalnews.com/tags/washington/" target="_blank">Washington</a> to try to persuade US president-elect <a href="https://www.thenationalnews.com/tags/donald-trump/" target="_blank">Donald Trump</a>’s team to fulfil a deal that will give Mauritius sovereignty over the Chagos Islands. Jonathan Powell, who negotiated the agreement in return for retaining control of a joint<a href="https://www.thenationalnews.com/tags/uk/" target="_blank"> UK</a>-US military base on Diego Garcia, plans to visit Washington within the next few days. A UK government spokeswoman reiterated to<i> The National</i> that Labour is working "very closely" with the current US administration, and will continue to do so with Mr Trump's government. On Wednesday, Number 10 said the government’s position on the Chagos deal “remains unchanged” and the UK is “finalising” the text of the treaty. Final details of the legal text of the treaty are being worked out, with the plan to put them before Parliament for scrutiny next year, they added. It follows reports by the BBC earlier this week that new Mauritian prime minister Navin Ramgoolam expressed reservations about the deal that was struck earlier this year, after a meeting with Mr Powell on Monday. Mr Trump, whose inauguration will take place on January 20, is believed to be looking for ways to scrap the agreement over security concerns about the base. Under the deal, the UK and<a href="https://www.thenationalnews.com/tags/us" target="_blank"> US </a>are believed to have secured the use of the airbase for at least 99 years. But <i>The Independent</i> reported that Mr Trump’s transition team has requested legal advice from the Pentagon owing to<i> </i>fears that <a href="https://www.thenationalnews.com/tags/china/" target="_blank">China</a>, an ally of <a href="https://www.thenationalnews.com/tags/mauritius/" target="_blank">Mauritius</a>, will be allowed to build a military installation on Chagos. Marco Rubio, who Mr Trump has picked to be secretary of state, previously warned the deal posed “a serious threat” to US national security. Reform UK leader Nigel Farage has reportedly encouraged Mr Trump’s team to investigate the consequences of the agreement before the election. “Diego Garcia was described to me by a senior Trump adviser as the most important island on the planet as far as America was concerned,” Mr Farage told MPs. But Mr Powell dismissed concerns about relinquishing control of the archipelago. He told Times Radio: “I don't think we should be too worried about losing that bit of territory. We're probably losing more to tidal erosion in the east coast [of England] than that.” Mauritius claims it was forced to give the Chagos Islands away in 1965 to gain its independence from Britain. The World Court said in 2019 that <a href="https://www.thenationalnews.com/world/britain-suffers-massive-defeat-at-un-over-disputed-chagos-islands-1.865129" target="_blank">the UK should give up control of the islands</a> and said it wrongfully forced the population to leave in the 1970s to make way for a US airbase. The UN's highest court, the International Court of Justice in The Hague, has ruled that Britain's administration of the territory is “unlawful” and must end. A report from the Policy Exchange think tank last year <a href="https://www.thenationalnews.com/world/uk-news/2023/10/26/britain-should-retain-chagos-islands-for-strategic-purposes-report-says/" target="_blank">argued that Britain should not relinquish sovereignty over the islands </a>in return for “an unenforceable promise by a third country that the military base at Diego Garcia will be allowed to continue to operate in the future”.