Bernie Sanders has launched a scathing criticism of the president following Trump's 'racist' remarks about 'rat infested' Baltimore - four years after he compared the city to a 'Third World Country'.

When Sanders was asked about the president's remarks, the senator said it was 'unbelievable that we have a President of the United States who attacks American cities, who attacks Americans, who attacks somebody who is a friend of mine.'

He told CNN: 'I do find it interesting that when we have rural Republican districts, the life expectancy is going down, where downtowns are boarded up, where people are struggling.

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Bernie Sanders on West Baltimore: "You would think that you were in a Third World country"https://t.co/JHxBxZjuNE — Trump War Room - Text TRUMP to 88022 (@TrumpWarRoom) July 27, 2019

Sanders' full comments at the time were: 'Anyone who took the walk that we took around this neighborhood would not think you're in a wealthy nation. You would think that you were in a Third World country'

'And people are struggling in rural America, they're struggling in urban America, they're struggling in suburban America.

Our job is to bring people together to improve life for all people, not to have a racist president who attacks people because they are African Americans. That is a disgrace, and that is why we're gonna defeat this president.'

But a clip recorded on the campaign trail in 2015, during Sanders' first attempt to lead the Democrats, captured the candidate suggest the area showed no signs of being within a developed economy, referring to infrastructure and jobs.

The clip was dug up by a Twitter account called Trump's War Room and was shared in the wake of the backlash Trump received for saying Rep. Elijah Cummings' district was rat 'infested.'

Sanders' full comments at the time were: 'Anyone who took the walk that we took around this neighborhood would not think you're in a wealthy nation. You would think that you were in a Third World country.

'But today what we're talking about is a community in which half of the people don't have jobs. We're talking about a community in which there are hundreds of buildings that are uninhabitable.'

The comments were not the first time Sanders singled out the congressional district for particular criticism. In 2016 he again used Baltimore as an example of the America's disproportionate distribution of wealth.

'Rep, Elijah Cummings has been a brutal bully, shouting and screaming at the great men & women of Border Patrol about conditions at the Southern Border, when actually his Baltimore district is FAR WORSE and more dangerous,' Trump tweeted

He tweeted at the time: 'Residents of Baltimore's poorest boroughs have lifespans shorter than people living under dictatorship in North Korea. That is a disgrace.'

On Saturday, Trump faced fierce backlash, including accusations of racism, after calling Cummings' congressional district 'a disgusting, rat and rodent infested mess.'

'Rep, Elijah Cummings has been a brutal bully, shouting and screaming at the great men & women of Border Patrol about conditions at the Southern Border, when actually his Baltimore district is FAR WORSE and more dangerous,' Trump tweeted.

On Saturday, Trump faced fierce backlash, including accusations of racism, after calling Cummings' congressional district 'a disgusting, rat and rodent infested mess'

'His district is considered the Worst in the USA as proven last week during a Congressional tour, the Border is clean, efficient & well run, just very crowded. Cumming District is a disgusting, rat and rodent infested mess. If he spent more time in Baltimore, maybe he could help clean up this very dangerous & filthy place,' he said.

Leading Democrats called Trump's tweets racist including House Speaker Nancy Pelosi and Sen. Elizabeth Warren, a 2020 candidate for president.

Baltimore Mayor Bernard Young said Trump is 'a disappointment to the people of Baltimore, our country, and to the world.'