The top White House official in the war against drugs says he is optimistic about fighting the global trade in illegal substances.

The White House's so-called "drug czar," John Walters, says the war against drugs and the terrorists who traffic them is at a turning point.

"We are not there yet, but we know what has to be done and we have the conditions for doing successful things in the coming five to 10 years," he said.

Mr. Walters says drug traffickers and terrorists move hundreds of metric tons of illegal substances in and out of the United States undetected. The cost of that trade, he says, is tremendous.

"It is not acceptable... that the American drug consumer is the single largest funder of anti-democratic forces in this hemisphere," said Mr. Walters. "I am not making the argument that all global terrorist groups get money from drugs. That is not true. But, almost half of the State Department's list of known terrorist organizations are known to have in one way or another trafficked in drugs."

Mr. Walters, who directs the Office of National Drug Control Policy, says until authorities can shut down the movement of drugs throughout the world, Americans will not feel secure.

But the drug expert says he is optimistic about reaching that goal. He says right now, there is an historic opportunity to change things for the better in many regions of the world.

In South America, he says Colombian President Alvaro Uribe has more than met promises he made to fight cocaine production. Mr. Walters says Colombia, the world's largest producer of the drug, reduced production by 15 percent last year, and sprayed more than 100,000 hectares of the coca plant.

"We believe with the current rate of decline we should begin to see substantial changes in the availability of cocaine throughout the world in the next six to 12 months," Mr. Walters said.

He added that although Bolivia and Peru have more work to do, those governments are working more closely with the United States as well.

Mr. Walters says in South Asia, Afghanistan's opium trade remains the biggest threat. But even there, he says dialogue is now possible where it was not a decade ago, and production is down.

"The last report was that production in Afghanistan will be half of what it was at the peak of the Taleban regime," he said. "That is good for the world."

Mr. Walters says in other parts of the globe, countries are beginning to realize that the consequences of looking the other way are intolerable. He says the Chinese government has been advocating stronger international cooperation and tougher laws against the synthetic drug trade, because it has become a national security threat there.