The wheels of Air Force One hadnt even touched the ground at the airport when Donald Trump announced his arrival to the UK by tweeting about London Mayor Sadiq Khan.

Not content with comments he made last night about the mayor, the president repeated them and for good measure called him a stone cold loser as well.

In two tweets, he wrote: Sadiq Khan, 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.

He is a stone cold loser who should focus on crime in London, not me......

He added: Kahn reminds me very much of our very dumb and incompetent Mayor of NYC, de Blasio, who has also done a terrible job - only half his height.

In any event, I look forward to being a great friend to the United Kingdom, and am looking very much forward to my visit. Landing now!

Khans spokesman responded by saying childish insults should be beneath the president of the United States.

They added: Sadiq is representing the progressive values of London and our country, warning that Donald Trump is the most egregious example of a growing far-right threat around the globe, which is putting at risk the basic values that have defined our liberal democracies for more than 70 years.

Later Monday, New York Mayor Bill de Blasio came out in support of Khan.

On Sunday, Khan stoked the ire of the president by describing him as just one of the most egregious examples of a growing global threat and compared the language he has used to that of the fascists of the 20th century.

As he left the White House on that evening, Donald Trump rebuked the mayor of London and said he would not be willing to meet him.

Raising the stakes even further, Trump praised former Foreign Secretary Boris Johnson , who is widely tipped to become the next prime minister after Theresa May steps down, and Brexit Party leader Nigel Farage. Trump also talked up the prospect of a Brexit trade deal, rebuked and denied making bad comments about the Duchess of Sussex as he set off for Britain even though hes on tape making them.

Trump said he expected his three-day state visit to be very important and very interesting as he left the White House.

Mondays itinerary includes a ceremonial welcome at Buckingham Palace followed by a visit to the Royal Collection and then an event at Westminster Abbey.

Later the president and first lady Melania Trump will have tea with the Prince of Wales and Duchess of Cornwall, followed by a state banquet.

This story has been updated with Khans and de Blasios responses.