The US government estimates that heroin production has sharply declined in Colombia over the past decade, yet the United Nations claims the country remains the primary supplier of the drug for the US market. So which is it? The picture is confusing, beginning with the most recent World Drug Report from the United Nations Office on Drugs and Crime (UNODC). In the report, the UN said Colombia continued to be reported by US officials as the main supplier of heroin to the United States.