London Mayor Sadiq Khan's war of words with Donald Trump escalated after he called on Britons to take to the streets in a show of "freedom of speech" the president's visit.

Trump is set to visit the U.K. in July, it was announced on Thursday. He had previously canceled a trip to Britain over concerns in Washington that his visit would prompt protests.

"If he comes to London, President Trump will experience an open and diverse city that has always chosen unity over division and hope over fear," Khan tweeted Thursday. "He will also no doubt see that Londoners hold their liberal values of freedom of speech very dear."

Speaking to British radio station LBC on Friday, U.S. Ambassador Woody Johnson confirmed that Trump would "definitely be coming to London."

Khan is the first Muslim mayor of any major Western capital city.

Khan and Trump have a history of exchanging barbs.

In November, Khan said Trump was not welcome in London after the president used his Twitter account to share anti-Islam videos from a U.K. far-right group.

In June, Trump lashed out at Khan for his response to a terror attack in which eight people died. Khan criticized Trump in January 2017 over his ban on travelers from Muslim countries, despite Trump suggesting that he would consider Khan an "exception."