“When somebody attacks my city, our citizens, our values, our way of life — when somebody makes certain generalisations about the followers of one faith — I think it’s incumbent to stand up to them,” he declared.
Mr Trump branded the Lord Khan a “horrible, vicious, disgusting mayor” who had done a “terrible job”.
Their feud led the US President to demand that the London Mayor not be invited to the State Banquet at Windsor Castle during his state visit last year, saying aboard Air Force One: “I didn’t want him there, I asked that he not be there.”
The feud between the two men has endured for more than 10 years, beginning with Mr Trump announcing his plan to block Muslims from entering the United States during his first successful campaign to take the White House in 2015.
Over the years, the pair have regularly traded blows on social media and in media interviews.