The next phase in the fight against illicit methamphetamine should emphasize tightening U.S. borders to prevent drug trafficking, expanding voluntary drug testing in schools, and augmenting treatment for addicts, the nation's drug czar said Tuesday.

"Today we have to learn that meth is both a problem on the preventative side and the supply side," John P. Walters, director of the White House drug policy office, said during a news conference in western North Carolina where law officers have raided hundreds of meth labs in recent years.

Restrictions on the sale of cold medicines with ingredients used to make meth have helped several states significantly reduce the number of meth labs in operation, government officials say.

But the gains made by shutting down local meth labs are now threatened by trafficking from super-labs in California and Mexico, officials say.

Meth addiction often leads to psychotic or violent behavior and brain damage. People high on the drug will often stay awake for days.

Walters said the federal government supports expanding random drug testing in schools, an existing program that would remain voluntary. He said research shows that youths who don't use drugs and alcohol are less likely to get hooked after age 20.

"We can change this problem in a durable way for years and years by reducing exposure to young people," Walters said in an interview with The Associated Press.

He also said his office supports boosting federal money for treatment programs.