Amaral Duclona, one of the gang leaders in Cite Soleil, a warren of cement block homes and shanties on the outskirts of the capital, said: "UN troops don't want peace and disarmament because they want a justification for their presence here."
Duclona, acting as a spokesman for all the gangs in Cite Soleil, said there were no plans for a rescheduling of Monday's public ceremony, during which he and other gang leaders were to carry out a pledge made last week to lay down their arms.
Rene Preval, Haiti's president, and Edouard Alexis, the prime minister, have demanded that all armed gangs surrender their weapons or risk being killed. But Duclona said UN peacekeepers had become an obstacle to peace.
"How can we hand over our weapons while UN troops continue to conduct heavy attacks against us?"
The gangs in Cite Soleil, which is home to thousands of supporters of Jean-Bertrand Aristide, the former president, were mostly responsible for violence aimed at destabilising the US-backed interim government installed after Aristide was ousted from power in February 2004.
The United Nations sent its peacekeeping force - now numbering about 8,000 soldiers and police - to restore order shortly after Aristide was pushed from office by an armed rebellion.
The level of violence dropped after Preval, a former Aristide protege, was elected in February. But kidnappings and political bloodshed have risen again since last month.