VIENNA, Austria -- The international community is making significant strides toward ridding northern Afghanistan of opium, a U.S. counter-narcotics official said Friday, despite setbacks in the Taliban-controlled south and forecasts of another record year of poppy cultivation.

Tom Schweich, the U.S. principal deputy assistant secretary for international narcotics, said rapid assessment surveys conducted earlier this year showed a "dramatic" decrease in poppy growing in Afghanistan's northern provinces.

In a few years, "we hope the entire northern half of Afghanistan will be opium-free," Schweich told reporters after meeting with Antonio Maria Costa, head of the U.N. Office on Drugs and Crime.

But Schweich conceded the situation remains bleak in southern Afghanistan, where poppy cultivation is up 10-50 percent in a half-dozen key provinces -- feeding concerns that the country is swiftly becoming a narco-state.

Marvin Weinbaum, an expert on Afghanistan at the Middle East Institute in Washington D.C., warned Friday that unless there is also a decrease in poppy growing in southern Afghanistan, "there is nothing to be proud about."

"We have to look at the bottom line here, not just at a few provinces," said Weinbaum, a former State Department analyst on Afghanistan. "The initial indications in terms of net production are that there will not be a decrease of opium production in Afghanistan."

The U.N. drug office warned earlier this week that 2007 cultivation could expand again after last year's record crop, which spiked upward by 59 percent. Experts say booming profits from the lucrative crop are being used to fuel the Taliban insurgency.

"Afghanistan is the No. 1 drug problem in the world ... the rise in opium production is alarming," Schweich said. "The drug trade is causing tremendous amounts of political corruption and is causing economic problems."

Surveys taken in the northern provinces of Balkh, San Pul, Samangan, Bamyan and Ghor show a "strong decrease" in cultivation of poppy that yields opium, the raw material for heroin, and several other provinces, including Parwan, Wardak, Logar, Paktya and Paktika, are considered "poppy free," Schweich said.

"It shows that it's working up in the north," he said, adding that decreases were recorded in provinces where local governors made it a priority to get farmers to grow other, legal crops.

In the south, however, surveys showed strong increases in cultivation "in virtually every area," Schweich said, adding that he toured southern Afghanistan about a month ago.

He said the U.S. and its allies were working to develop a network of informers who could help pinpoint storage locations for harvested poppy so those sites could be destroyed.

The security situation in the south has impeded efforts to discourage cultivation, wipe out fields and arrest and prosecute traffickers, he said.

Among the provinces registering a sharp increase was Helmand, Afghanistan's largest poppy-growing region and an area where the Taliban repeatedly has attacked NATO convoys.

This week in Helmand, NATO and Afghan troops launched the alliance's largest-ever offensive in Afghanistan.