The British ambassador to the U.S. resigned on Wednesday, days after leaked cables that criticized President Trump Donald John TrumpSteele Dossier sub-source was subject of FBI counterintelligence probe Pelosi slams Trump executive order on pre-existing conditions: It 'isn't worth the paper it's signed on' Trump 'no longer angry' at Romney because of Supreme Court stance MORE escalated tensions between the two close allies.

Kim Darroch’s resignation came one day after Trump bashed him as a “very stupid guy” and “pompous fool” and his tenure became a flashpoint in the race to replace outgoing British Prime Minister Theresa May Theresa Mary MayAre US-Japan relations on the rocks? Trump insulted UK's May, called Germany's Merkel 'stupid' in calls: report Bolton says Boris Johnson is 'playing Trump like a fiddle' MORE.

ADVERTISEMENT

“Since the leak of official documents from this Embassy there has been a great deal of speculation surrounding my position and the duration of my remaining term as ambassador. I want to put an end to that speculation. The current situation is making it impossible for me to carry out my role as I would like,” Darroch wrote in his resignation letter, released by the U.K. Foreign Office.

Foreign Office chief Simon McDonald said he accepted Darroch’s resignation with “deep personal regret.”

Darroch’s blunt assessment of the president and his administration appeared in diplomatic cables intended for a private audience of senior officials in London. But the documents were leaked and published in a U.K. newspaper on Sunday.

The ambassador described the Trump administration as “clumsy and inept” and wrote that Trump was “radiating insecurity,” adding that his presidency could end in “disgrace and downfall.”

Trump reacted angrily, saying Monday that he would “no longer deal” with Darroch and suggested things could change once Britain selects a new prime minister. He also lashed out at May, saying she handled Brexit in a “foolish way.”

The president froze the ambassador out of a Monday night dinner with the emir of Qatar and other meetings with top advisers, including Trump’s daughter Ivanka, were scrapped.

By resigning now, Darroch could allow May to choose his replacement before she steps down at the end of the month.

The British government has defended Darroch in the days following the leak, saying that diplomats must offer frank assessments in the country where they serve.

Foreign Secretary Jeremy Hunt, one of the candidates vying to replace May, said the president’s comments were “disrespectful” and vowed to keep Darroch on board in Washington.

Hunt said Wednesday that he is “deeply saddened” by Darroch’s resignation and expressed outrage “that a selection of his reports should have been leaked.”

But his main rival, Boris Johnson, declined to condemn Trump and was noncommittal about keeping the ambassador. A staunch support of Brexit, Johnson has touted his close ties to Trump and the White House to argue he can secure a trade deal with the U.S.

--Kyle Balluck and John Bowden contributed to this report, which was updated at 8:13 a.m.