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.

“Democrats are the problem,” he wrote. “They don’t care about crime and want illegal immigrants, no matter how bad they may be, to pour into and infest our Country, like MS-13.”

The violent gang La Mara Salvatrucha, also known as MS-13, formed decades ago among Salvadoran immigrants who immigrated to Los Angeles primarily among Salvadorans. The gang became international when many of those members were deported back to Central America, giving the gang a foothold there. There are an estimated 30,000 members worldwide and 10,000 in the US, per the Justice Department.

Though known for brutal killings, often with machetes or stabbings, MS-13 remains a small fraction of the overall gang problem in the US, according to FBI statistics. Victims tend to be members of the immigrant community, rival gang members or individuals who spurned the gang.

The Trump administration has vowed to “destroy” MS-13, which Attorney General Jeff Sessions has called “one of the gravest threats to American public safety.”

CNN’s Tal Kopan, Betsy Klein and Kevin Liptak contributed to this report.