Trump, First Lady Meet Queen at Buckingham Palace

President Donald Trump met with Queen Elizabeth II Monday during a three-day visit to Britain meant to strengthen ties between the two nations, although the trip was immediately at risk of being overshadowed by Brexit turmoil and Trump's feud with London's mayor.

Trump and first lady Melania Trump flew to Buckingham Palace in Marine One, landing on a lawn where they were greeted by Prince Charles and his wife Camilla. They received a royal gun salute as they walked to the palace where the queen greeted the president with a smile.

Even before Air Force One touched down north of London, Trump unleashed a Twitter tirade against London Mayor Sadiq Khan, leader of the world city where Trump will stay for two nights while partaking in a state visit full of pomp and circumstance.

The move came after a newspaper column in which Khan said Trump did not deserve red-carpet treatment in Britain and was "one of the most egregious examples of a growing global threat" from the far-right to liberal democracy.

"@SadiqKhan, who by all accounts has done a terrible job as Mayor of London, has been foolishly "nasty" to the visiting President of the United States, by far the most important ally of the United Kingdom," Trump wrote just before landing. "He is a stone cold loser who should focus on crime in London, not me.

The president added that Kahn reminded him of the "terrible" leader of his hometown, New York City Mayor Bill de Blasio though "only half his height." De Blasio, a Democrat, is a longshot candidate in the 2020 presidential race. Khan supporters have previously accused Trump of being racist against London's first Muslim mayor.

The president then added a few warm words for his hosts, tweeting that he was looking forward "to being a great friend to the United Kingdom, and am looking very much forward to my visit."