Colombian military and police also use U.S.-provided weapons and equipment, an agreement that came under scrutiny earlier this year after police there killed multiple protesters during demonstrations against government tax proposals. A related analysis by The Post, published in May, found that Colombian authorities overstepped their own rules of engagement in some of the deadly encounters.

Fighting in Colombia’s decades-long war has been a springboard for military veterans to trade their U.S.-funded experience for hire in other global conflicts, such as in Yemen.

“The recruitment of Colombian soldiers to go to other parts of the world as mercenaries is an issue that has existed for a long time, because there is no law that prohibits it,” the commander of Colombia’s armed forces, Gen. Luis Fernando Navarro, told reporters last week.

Foreign military training provided by the United States is intended to promote “respect for human rights, compliance with the rule of law, and militaries subordinate to democratically elected civilian leadership,” Hoffman, the Pentagon spokesman, said in his statement. He did not immediately respond to questions seeking additional information.

The disclosure that some of the assassination suspects received U.S. training, which has not been previously reported, is certain to complicate the already murky understanding of how the plot to kill Moïse took shape, and who was involved.

Two U.S. citizens of Haitian descent are among those who have been arrested, and Haitian authorities identified five companies associated with the case, including CTU Security, based in Florida. Colombian police also identified 19 plane tickets purchased by a company credit card registered in Miami. The tickets were used by some of the 21 Colombian suspects to travel from Bogotá, Colombia, to Santo Domingo, Dominican Republic, authorities said.

Christian Emmanuel Sanon, 63, an American doctor and pastor who frequently traveled between Haiti and Florida, was arrested in connection with the plot. Authorities have claimed he was positioning himself to run for president in the impoverished Caribbean nation and had a role in hiring the alleged assassins, but they have provided little evidence about his alleged involvement.

To date, Haitian authorities have arrested at least 20 people in connection with Moïse’s death, which has plunged the country into a leadership crisis. Late Wednesday, officials confirmed they had detained the presidential palace’s head of security.

Authorities in Haiti are investigating Moïse’s killing with assistance from the FBI, Department of Homeland Security officials and personnel from Colombia’s government. President Biden has condemned the assassination and appealed for calm, but his administration has rebuffed requests from Haiti’s government for American military assistance to help shore up security.

Samantha Schmidt, Widlore Merancourt, Rachel Pannett and Anthony Faiola contributed to this report.