London (CNN) London Mayor Sadiq Khan stood up for Rep. Ilhan Omar and the rest of "The Squad" as he joined dozens of British politicians in condemning US President Donald Trump's "blatant unashamed racism" against the four Democratic congresswomen.

Writing on Twitter on Thursday, Khan said the four women "represent hope for the future." The Mayor, who like Omar is Muslim, added that "their home is America, but their message crosses borders."

Khan, who has clashed with Trump on previous occasions, was also among British politicians who signed an open letter of solidarity along with almost 14,000 other signatories.

This was addressed to Omar, the Minnesota representative, and her three colleagues Rep. Rashida Tlaib of Michigan, Rep. Ayanna Pressley of Massachusetts and Rep. Alexandria Ocasio-Cortez of New York.

The letter, written by the campaign group Hope Not Hate and circulated on Thursday, said: "We are disgusted by Donald Trump's attack on you. His blatant, unashamed racism has appalled people around the world."

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