U.S. and U.N. experts agree that Afghanistan will harvest fewer poppy plants bound for the drug trade in 2008 after two years of record crops. But they have radically different estimates about what that decline will mean for opium production.

In a report obtained by The Associated Press ahead of its planned release Friday, the Bush administration claims that production of the heroin precursor will plunge by 31 percent, from 8,800 tons in 2007 to 6,100 tons this year. That''s more than five times the drop in production predicted by the United Nations in late August.

The White House Office of National Drug Control Policy maintains its estimate is accurate. Director John Walters says the U.N. report may contain "methodological anomalies" related to on-the-ground surveys of poppy fields and stocks and not factor the effect of poor weather into its production estimate.

The Vienna-based U.N. Office on Drugs and Crime, which compiled the U.N. report, was not immediately available to comment, but an official at its New York branch defended its estimate. The official spoke on condition of anonymity because he was not authorized to speak publicly on the matter.

When the U.N. report was released on Aug. 26, officials said that despite a 19 percent drop in cultivation, opium production would go down by only 6 percent because of a rise in yield in fields still under cultivation.