The United States says the amount of opium produced in Burma rose slightly in 2005, and the production of synthetic drugs also appeared to continue to grow.
In the State Department's 2006 International Narcotics Control Strategy Report, officials said the amount of land used to grow poppies for opium increased by 11% during the past year.
The report follows a United Nations study that said opium production fell by 26% in 2005. Despite the disagreement, officials said all studies indicate Burma's opium production remains some 80% below its peak a decade ago.
Burma is the second largest producer of illicit opium, but produces only a small fraction of that produced in Afghanistan -- the world's biggest opium exporter.
Officials said there continues to be a sharp increase in the production and export of synthetic drugs, such as crystal methamphetamine by drug gangs in border areas.
The State Department said Burma and Venezuela were the only two countries in the world that "failed demonstrably" to meet international counternarcotics obligations.