Haiti has asked for foreign troops to be sent to the country to protect key infrastructure after the assassination of President Jovenel Moïse.
The request was sent by the government to the US and the UN, but the US says it has no plans to offer military assistance "at this time".
Haitian police earlier said a group of 28 foreign mercenaries killed the president on Wednesday.
After a gun battle in the capital Port-au-Prince, 17 of them were detained.
Some of the group, which Haiti says included retired Colombian soldiers, were held at the house they were using, others after entering Taiwan's diplomatic compound, the police said.
Three suspects were killed by police, and eight others are still being sought.
The UN Security Council would have to approve any plan to send international troops to Haiti under UN auspices.
Although the US will not offer troops, it said on Friday it was sending FBI and Department of Homeland Security officials to Haiti to help in the investigation.
The killing has triggered some civil unrest in Haiti, the poorest nation in the Americas. A state of emergency remains in force across the country and it is unclear who is in effective charge of the country's government.
Firearms and cash
Bloodied and bruised, arrested suspects were shown to the media on Thursday, along with a slew of seized weapons.
It is still unclear who organised the attack and with what motive.
A number of questions remain unanswered, including how the alleged assassins were able to enter Moïse's home. His bodyguards are due to be questioned next week.
One prominent opposition figure has openly expressed scepticism over the current version of events. Former Haitian senator Steven Benoit told local station Magik9 radio on Friday it was "not Colombians who killed him", but did not provide evidence to back up his claims.
The attack took place in the early hours on 7 July, when gunmen entered the property, shooting him dead and wounding his wife. Mr Moïse, 53, was found lying on his back with 12 bullet wounds and a gouged eye, according to the authorities.
Martine Moïse, 47, was seriously wounded and is in a stable condition after being flown to Florida for treatment.
Police said the hit squad included mainly Colombians, along with two Haitian-Americans.
Found in the suspects' possession were firearms, sets of US dollar bills, the president's personal chequebook and the server that held surveillance camera footage from his home, Le Nouvelliste newspaper reported.
Taiwan confirmed that 11 of the suspects were arrested after breaking into a courtyard at its compound.
Angry civilians had joined the search for the gunmen, and helped police track down some who were hiding in bushes. The crowd set fire to three of the suspects' cars and destroyed evidence.
Police chief Léon Charles called for calm, saying the public should not take the law into their own hands.
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