"Look around. You go through certain areas that didn't exist 10 or 15 years ago", he said in an interview with The Sun newspaper.
Trump told the British tabloid that "allowing the immigration to take place in Europe is a shame".
Asked whether he thought that immigration was damaging the cultural fabric of the country - the question raised in relation to comments made by the President at a North Atlantic Treaty Organisation summit on Thursday and a previous interview in the British press - President Trump said: "I think it's been very bad for Europe".
U.S. President Donald Trump and British Prime Minister Theresa May are expressing differing views on the benefits of immigration to Europe.More news: China trade surplus with U.S. hits historic high & timing couldn’t be worse
Trump stressed his maternal Scottish and paternal German roots, declaring: "I have a great love for the countries of Europe". So I think allowing millions and millions of people to come into Europe is very, very sad.
Standing next to May at Chequers, the prime minister's official country estate, Trump acknowledged that his remarks were "politically not necessarily correct".
Telling British and American reporters gathered in the garden at her countryside residence that the United Kingdom "has a proud history of welcoming people" and that immigration has been good for the country.
It comes after the continent's migration crisis has made headlines yet again this year as hundreds of thousands of people - mostly from Africa and the Middle East - make risky journeys to reach Europe illegally.More news: British man poisoned with Novichok is no longer in critical condition - hospital
"I think it's changing the culture".
May says people of different backgrounds have contributed to her country's society, but it's important to have a "set of rules" when it comes to immigration. "I think they better watch themselves because you are changing culture". "I think they agree with me on immigration".
Khan said on Friday that he was "trying to rise above" the jibe, but when asked if the door of City Hall would be open to Trump if he wanted a face-to-face meeting, he added: "I'm happy to meet President Trump and to explain to him, in a respectful, courteous manner where I think he's wrong on a number of issues, to hear him out, see what his explanation is for holding me responsible for the attacks we saw in London past year".More news: George Clooney looks in pain after motorbike crash
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