Washington (CNN) President Donald Trump on Tuesday again invoked the imagery of undocumented immigrants as sub-human, this time to warn against the influx of gang members into the US.

Trump, who has often cited the dangers of the MS-13 gang to argue for tougher immigration laws, said there is an "infestation" of gangs in pockets of America.

"When we have an 'infestation' of MS-13 GANGS in certain parts of our country, who do we send to get them out? ICE! They are tougher and smarter than these rough criminal (elements) that bad immigration laws allow into our country. Dems do not appreciate the great job they do!" Trump tweeted Tuesday

The President's tweet also served his recent political strategy of defending Immigration and Customs Enforcement against calls from Democrats to "abolish" the agency and replace it in the wake of family separations at the border. Trump and the White House also have, without proof, repeatedly accused Democrats of protecting the rights of gang members and undocumented immigrants over those of American citizens.

Last month, Trump used similar language evoking images of pests, not human beings, in describing migrants approaching the US border.

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