U.N. chief details his proposal to help mission in Haiti fight gangs in a letter obtained by AP / On patrol with Kenyan forces inside Haiti's gang warzone / Under assault by gangs in Haiti, a Kenyan-led mission fights back / UN urges action as gang violence pushes Haiti to brink of state failure / Haitian gangs escalate violence and expand attacks outside the capital, top UN official says / UN extends Kenya-led force to tackle gangs in Haiti, but sidelines call for UN peacekeepers / Haitian leader supports creating UN-led mission to quell country's gang violence / As U.N. meets, Haitians express hopelessness at finding an international solution to gang crisis