(Bloomberg) — Prime Minister Boris Johnson’s government named Karen Pierce as the U.K.’s new ambassador to the U.S., filling a crucial post as it seeks to burnish post-Brexit ties with its closest ally.Pierce, 60, will be the U.K.’s first female ambassador to Washington, and will start her new role as soon as the U.S. government approves her appointment, Johnson’s spokesman, Jamie Davies, told reporters on Friday. Pierce will move to Washington from New York, where she’s been the envoy to the United Nations for the past two years.“It is a time of huge opportunity for the friendship between the U.K. and U.S. and I am delighted that Karen Pierce will take forward this exciting new chapter in our relationship,” Foreign Secretary Dominic Raab said in an emailed statement. “We’re proud to be sending to Washington such an outstanding diplomat, and I warmly congratulate her on her appointment.”The U.K.’s previous ambassador, Kim Darroch, quit in July after falling out with President Donald Trump, just one of a series of recent flash-points between the two sides that have come at a pivotal moment. Having left the European Union last month, Britain is trying to strengthen links with the world’s biggest economy by striking a trade deal this year.Trump Attacked U.K.’s Johnson Over Huawei in Heated Phone CallThe two governments have clashed in recent weeks on issues including Iran, U.K. plans to tax American technology companies, the involvement of a U.S. diplomat’s wife in a fatal car accident in England and the role of Huawei Technologies Co. in the U.K.’s next-generation broadband networks.Trump berated Johnson during a heated phone call after the prime minister rejected Washington’s request to ban Huawei from the U.K.’s 5G networks, according to a person familiar with the matter. The U.S. president had spent months trying to persuade the British government block the Chinese company on security grounds.It means Pierce must tread carefully while still fighting the U.K.’s corner. Her predecessor dramatically resigned after cables in which he called the Trump administration “inept” and “uniquely dysfunctional” were leaked, sparking a major diplomatic row. Trump froze out the envoy, saying he’d no longer deal with him.Johnson — then the front-runner in the race to succeed Theresa May as prime minister — notably failed to back Darroch, feeding into the envoy’s decision to resign. In a televised debate, Johnson would not commit to keeping Darroch in his job, in sharp contrast to the endorsements and support the ambassador received from May and other senior politicians.Pierce joined the Foreign Office in 1981 and has previously served as Britain’s ambassador to Afghanistan. She also appears to have made a good impression on Trump during her role as UN ambassador. After she attended a dinner with the president in early December, the Mail on Sunday reported he’d described her as “fab.”–With assistance from Jessica Shankleman.To contact the reporters on this story: Alex Morales in London at amorales2@bloomberg.net;Thomas Penny in London at tpenny@bloomberg.netTo contact the editors responsible for this story: Tim Ross at tross54@bloomberg.net, Stuart Biggs, Thomas PennyFor more articles like this, please visit us at bloomberg.comSubscribe now to stay ahead with the most trusted business news source.©2020 Bloomberg L.P.