White House press secretary Jen Psaki said Haiti's political leadership remains unclear and that it was vital for the country's leaders to come together to chart a united path forward.
"It's still under review," she said of Haiti's request to send troops. Asked if it had been ruled out, Psaki said, "No."
U.S. President Joe Biden told reporters later on Monday that his administration was "closely watching" developments in Haiti.
"The people of Haiti deserve peace and security, and Haiti's political leaders need to come together for the good of their country," Biden said.
Moise was shot dead early on Wednesday at his Port-au-Prince home by what Haitian authorities describe as a unit of assassins including 26 Colombians and two Haitian-Americans. Haitian police said on Sunday they had arrested another suspect.
A separate U.S. government source said on Monday that at least one of the Haitian-Americans arrested on suspicion of taking part in Moise's killing had been an informant for the U.S. government law enforcement agency. read more
The death of the president plunged the troubled country into deeper turmoil, and U.S. officials traveled there on Sunday to assess the situation and meet three politicians who have all staked competing claims to take charge. read more
"What was clear about their trip is that there is a lack of clarity about the future of political leadership," Psaki said at a news briefing.
Haitians in the capital Port-au-Prince were planning protests this week against Joseph, according to social media posts. Joseph's right to lead the country has been challenged by two other senior politicians, Prime Minister-Designate Ariel Henry and Senate President Joseph Lambert.
The political turmoil could worsen longstanding poverty and lawlessness for most Haitians if the acting government only focuses on the investigation into Moise's killers, said Feckenson Cheri, 33, who lives with his aunt in the capital.
"I know they're arresting the people they think killed the president, but I'm not sure they'll ever figure it out. What we need is help to save us from the misery that's all around us," he said.
Emily Horne, a spokesperson for the U.S. National Security Council, said the U.S. delegation held a joint meeting with Joseph and Henry, and a meeting with Lambert to "encourage open and constructive dialogue" to reach an agreement to enable Haiti to hold free and fair elections, Horne said.
On Sunday, Haitian police said they had detained a suspected plot mastermind, 63-year-old Christian Emmanuel Sanon, widely described as a Florida-based doctor, whom authorities accuse of hiring mercenaries to oust and replace Moise. read more
On Monday, Haitian police issued an arrest warrant for a Colombian, apparently in connection with the alleged plot. Colombian media said the man was a retired soldier.
Colombian police said on Monday they could not share any hypothesis about the death of Moise and that they respect the Haitian state's autonomy. So far 18 Colombians tied to the case have been arrested and three more killed.
Families of some of the Colombians, many ex-soldiers, have said their relatives were hired as bodyguards, not as mercenaries, and that they did not kill Moise. read more
The men were initially contracted to protect Sanon and were later presented with a warrant to arrest Moise, Haiti's National Police Chief Leon Charles said Sunday.
Photos said to be of Sanon meeting with a group of men, including another suspect in the case, Haitian-American James Solages, began circulating on social media late on Sunday. Reuters could not verify the authenticity of the images.
A man by Sanon's name is listed online as a doctor who has worked in Florida, where a security company that Haitian authorities say hired suspects in the case is based.
Colombian authorities are investigating Herard's activities during his visits, Colombian police chief Jorge Luis Vargas said.
High-ranking Colombian intelligence officials have been in Haiti since Friday to assist with the investigation. Reporting by Jeff Mason in Washington, Luis Jaime Acosta in Bogota and Andre Paultre and David Alire Garcia in Port-au-Prince Additional reporting by Mark Hosenball, Patricia Zengerle, Doina Chiacu and Daphne Psaledakis in Washington Writing by Julia Symmes Cobb and Patricia Zengerle; Editing by Alistair Bell and Cynthia Osterman