Haiti’s interim prime minister Claude Joseph, who has run the country following the assassination of president Jovenel Moise, will step down and hand power to his internationally-backed rival, Ariel Henry, it has been announced.

Mr Joseph and Mr Henry have been engaged in a bitter power struggle since the country was thrown into turmoil on July 7, when Moise was gunned down in his own home.

Mr Henry was due to take over as prime minister that week, but Mr Joseph declared a “state of siege” and said that he was still in charge.

Haiti had no working parliament and no workable succession process, and was already mired deep in a political and security crisis when Moise was killed.

But on Saturday, the important Core Group of international ambassadors and representatives urged "the formation of a consensual and inclusive government," and backed 71-year old neurosurgeon, Mr Henry to lead.

Claude Joseph had been running the country since the assassination of Jovenel Moise

Credit: Valerie Baeriswyl / AFP)

Under heavy pressure from the ambassadors and representatives from Germany, Brazil, Canada, Spain, the United States, France and the European Union, Mr Joseph has backed down.

He told the Washington Post on Monday: "Everyone who knows me knows that I am not interested in this battle, or in any kind of power grab.

"The president was a friend to me. I am just interested in seeing justice for him.”

Mr Joseph said that he and Mr Henry had met privately over the past week, adding that he agreed to step down on Sunday "for the good of the nation."

Mr Henry said in a statement: “I give the reinsurance that light will be shed and those who carried out [the assassination] and its intellectual authors will be brought to justice.”

On Tuesday, a new government will be formed with Mr Henry as prime minister. Mr Joseph will return to his former post as foreign minister.

The new government will not have a president, and will be tasked with organising fresh elections as soon as possible.

So far 18 of the 26 Colombians suspected of playing a role in the attack have been detained, while three were killed by police and five are still on the run. 

Police have also arrested two Haitian Americans and another Haitian thought to be the brains behind the operation.

Dimitri Herard, the head of palace security for Moise, has also been arrested. Prosecutors want to know why the attackers did not meet more resistance at the president’s home.

Mr Moise’s wife, Martine, arrived in Haiti on Saturday aboard a private jet clad in black and wearing a bulletproof vest. 

She had been treated in hospital in Miami for gunshot wounds sustained when the armed gang stormed her home.

She has not issued a statement or spoken publicly as the government prepares for the July 23 funeral that will be held in Port-au-Prince.