Trump has cited drug cartels as a primary reason for ramping up his administration's involvement in the Americas, pressuring Venezuela over the past several months and seizing Venezuelan President Nicolas Maduro in January.
At least a dozen leaders from Central America, South America and the Caribbean joined the "Shield of the Americas" summit convened by Trump, who signed a proclamation launching the coalition.
"It's a great part of the world but to fill that tremendous potential, we must smash the grip of the cartels and criminal gangs and horrible organisations run by, in some cases, absolute animals and truly liberate our people," Trump said.
Kristi Noem will be special envoy for the "Shield of the Americas", Trump posted on Thursday.
Noem was Homeland Security secretary until Trump removed her from that post this week after mounting criticism of her from Congress.
Saturday's gathering brings together centrist and conservative leaders aligned with Trump on security, migration and economics.
Among those attending are Argentine President Javier Milei, Chile's president-elect Jose Antonio Kast and Salvadoran President Nayib Bukele, whose gang crackdown, criticised by human rights groups, has become a model for some in Latin America.
Politicians from across the region have toured Bukele's sprawling "mega-prison," where the United States last year deported more than 200 Venezuelans without trial.
Also joining the gathering are Honduran President Nasry Asfura, who narrowly won a disputed election with Trump's backing, and Ecuador's President Daniel Noboa, who has echoed parts of Trump's economic agenda and recently announced joint operations with the US in a military crackdown on drug trafficking.
