The Bush administration has been accused of ignoring its own arms embargo and overseeing the sale of $7m-worth (£3.7m) of weapons to the Haitian government to equip its police force.
Human rights groups say the police carry out routine executions of dissidents and weapons are often illegally funnelled to armed militia.
Robert Muggah of the Swiss-based Small Arms Survey, a non-profit group, said that last year the US effected the sale of thousands of weapons to the interim government headed by Gerard Latortue, despite a 13-year arms embargo. "They are meant to brace up a shaky security force, but the reality is they could actually undermine security by jeopardising an innovative disarmament effort just getting under way," said Mr Muggah, who has spent several months in Haiti interviewing diplomats and UN officials for a report.
The embargo was established after a coup that ousted the elected president Jean-Betrand Aristide, who was forced into exile for a second time last year. Washington, which had long under- mined his presidency, refused to help him. The weapons embargo remains in place.
Mr Latortue, installed following negotiations involving the US, France and Canada, complained the ban prevented him equipping the police.
But according to Mr Muggah, despite Mr Latortue's public protestations, a number of arms sales have gone ahead. His report says 5,435 "military-style weapons", including M-14 and other semi-automatic guns and 4,433 handguns worth $6.95m, were provided from the US.
Haiti is already awash with guns and violence. Human rights groups say supporters of Mr Aristide's political party, Lavalas, have been subjected to violence and oppression. The Haitian National Police (HNP) is also accused of carrying out a campaign of violence in the slums of the capital, Port-au-Prince.
Brian Concannon, a lawyer with the Institute for Justice and Democracy in Haiti (IJDH), which has links to the former government, said: "It is well-documented that the Haitian police routinely execute political dissidents and suspected criminals, so with them the guns are already in the wrong hands.
"But many officers - especially those illegally integrated from the rebel army - funnel arms to paramilitary groups that are even more brutal."
A recent report by the human rights programme at Harvard Law School said HNP membe