Donald Trump has claimed he banned Sir Sadiq Khan from attending events put on for his second state visit to Britain.
The US president reportedly told how he personally demanded London's Mayor be sidelined despite wanting to be there.
Speaking to reporters on Air Force One, Mr Trump said: "He wanted to be there, as I understand it. I didn't want him. I didn't want him there. I asked that he not be there.
"I think the Mayor of London, Khan, is among the worst mayors in the world and we have some bad ones. I think he's done a terrible job."
The pair's war of words dates back to 2017, when the president criticised the mayor's response to the London Bridge terror attack.
On the eve of Mr Trump's return to the White House in January, Sir Sadiq warned of "resurgent fascism" and echoes of 1930s Germany.
The president responded in July while staying at his Turnberry golf course in Scotland, by branding the Mayor a "nasty person" who was doing a "terrible job".
Before Mr Trump arrived at Stansted Airport on Tuesday for his unprecedented second state visit, Sir Sadiq had written a blistering attack against the president.
Writing in the Guardian, he accused the Republican of fuelling "divisive, far-Right politics around the world".
He said: "Scapegoating minorities, illegally deporting US citizens, deploying the military to the streets of diverse cities. These actions aren't just inconsistent with Western values - they're straight out of the autocrat's playbook."
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