CNN anchor Victor Blackwell.

A newsreader broke down on air as he blasted Donald Trump for dismissing his majority black home city in what he claimed were racist terms.

Victor Blackwell rebuked the US President over his attack on Elijah Cummings, a Baltimore congressman whose district has a population that is over 50% black.

CNN anchor Mr Blackwell blasted Trump for calling the city a “disgusting, rat and rodent-infested mess”.

Fighting tears, he said: “Donald Trump has tweeted more than 43,000 times. He’s insulted many different types of people.

"But when he tweets about infestation, it’s about black and brown people.”

Civil rights leader Mr Cummings has initiated several probes into the Trump administration’s policies in his role as chairman of the House Oversight Committee, including its handling of migrants at detention centres.

Trump labelled him “a brutal bully” presiding over a city where “no human being would want to live”.

Donald Trump. Photo: Courtesy.

But Mr Blackwell defended the Maryland city, saying: “People get up and go to work there, they care for their families there, they love their children who pledge allegiance to the flag. They are Americans too.”

Nancy Pelosi led Democrats in defending Mr Cummings, saying: “We all reject racist attacks against him.”

Baltimore mayor Bernard Young said: “We have rats all over the country. We have two-legged rats.”

Trump’s attack came after US news show Fox & Friends accused Mr Cummings of focusing on migrants more than his constituents.

Over footage of struggling areas of Baltimore, it said: “Living conditions at the border are better than most areas in his district.”