Just moments before landing in England for his second state visit to the United Kingdom, President Trump revitalized his ongoing war of words with London Mayor Sadiq Khan. Mr. Trump tweeted early Monday aboard Air Force One, slamming Khan as doing a "terrible job" as mayor and later called the Briton "nasty," a term he's quoted as using to describe the Duchess of Sussex, Meghan Markle.

"He is a stone cold loser who should focus on crime in London, not me," Mr. Trump wrote of Khan. It's a refrain the president has used many times over, including during his previous state visit to the UK. Mr. Trump first knocked Khan for his "political correctness" in the wake of a deadly terror attack in London in 2017.

"We must stop being politically correct and get down to business of security for our people," Mr. Trump tweeted. The two then got into a heated Twitter exchange after Khan said he was "reassured" London was on of the "safest global cities in the world."

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In response, Mr. Trump tweeted, saying, "At least 7 dead and 48 wounded in terror attack and Mayor of London says there is 'no reason to be alarmed!'" He later posted, "Do you notice we are not having a gun debate right now? That's because they used knives and a truck!"

He also compared Khan to that of "very dumb and incompetent" New York City mayor and 2020 contender Bill de Blasio, a comparison de Blasio, self-desrcibed "Khan stan" considered a "compliment."

....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! — Donald J. Trump (@realDonaldTrump) June 3, 2019

The long simmering feud between Mr. Trump and Khan, a Muslim who was elected as London's mayor in May 2016, started after Khan's election. Khan tweeted criticism of then-candidate Trump's rhetoric, saying that his "ignorant view of Islam could make both our countries less safe. It risks alienating mainstream Muslims." President Trump later challenged Khan to an IQ test during an interview on Britain's ITV.

Khan later replied to the president's attacks by tweeting a video where he publicly denounced the U.S. president's rhetoric and policies. In a video released in partnership with Elle UK, Khan directed his message right to Mr. Trump, saying his values are the "complete opposite of London's values and the values in this country."

Regardless of the twitter tit-for-tat, Mr. Trump appeared optimistic of his visit to the UK, saying he looked forward to being a "great friend" to longtime U.S. ally, even if CNN is the "primary source of news available from the U.S." according to his assessment.