US authorities have charged a retired Colombian soldier over the assassination of Haiti's President Jovenel Moise last July, justice officials said Tuesday.

The Justice Department said in a statement that 43-year-old Mario Palacios, along with others, "participated in a plot to kidnap or kill the Haitian President."

Palacios was detained at a Panamanian airport late Monday and flown to Miami as part of a "voluntarity extradition" deal.

If convicted, Palacios faces a maximum sentence of life imprisonment. He was taken into custody and was scheduled to appear in a Miami court later Tuesday.

US prosecutors said the plot against Moise "initially focused on conducting a kidnapping of the president as part of a purported arrest operation," but it "ultimately resulted in a plot to kill."

Prosecutors alleged in their complaint that "on July 7, 2021, Palacios and others entered the president's residence in Haiti with the intent and purpose of killing President Moise, and in fact the president was killed."

Others involved in the plot were 20 Colombian citizens and a group of Haiti-based dual Haitian-American citizens, according to statement.

Palacios had been on his way to Colombia after being deported by Jamaica for a lack of evidence connecting him to the assassination, but he was arrested during a stopover at Tocumen International Airport in Panama.

In this file photo taken in October 2021, a group of activists demands justice for slain Haitian president Jovenel Moise
In this file photo taken in October 2021, a group of activists demands justice for slain Haitian president Jovenel Moise AFP / Richard PIERRIN

After his arrest, Palacios "accepted voluntary extradition, so last night (Monday) he boarded a flight to Miami," Panama migration service head Samira Gozaine said, adding that there was an Interpol warrant out for the ex-soldier on "charges of murder and conspiracy to kill."

Moise was shot on July 7 at his home in Port-au-Prince.

Three Colombians were killed by Haitian armed forces responding to the attack and 18 more were detained, alongside two US citizens of Haitian descent.

Dozens of people have since been arrested, but the authors of the attack remain unknown.

The assassination deepened an already dramatic crisis in Haiti, which is suffering from a lack of security, soaring gang violence and a spate of kidnappings.

Haitian Prime Minister Ariel Henry, who has in effect been running the country since Moise's killing, told AFP on Monday that he too had been targeted in an assassination attempt, during last weekend's national day celebrations.

On Tuesday he welcomed the charges against Palacios in a brief statement.

"Prime Minister Ariel Henry wants justice to prevail ... not only for the former President but also his family as well as our nation," his office said.