Gil Kerlikowske, the US drug czar, said that as cocaine use falls in the United States and security is tightened on its border with Mexico, more drugs are flowing toward Africa. Despite this, he warned that Americans should not be complacent about the shift.

Hugh Bronstein of Reuters reports that the United States and Mexico are cracking down on cartels locked in a bloody war for control of the multibillion-dollar cocaine trade, and U.N. experts say U.S. consumption has fallen significantly.

These changes have pushed more of the trade in South American cocaine toward West Africa for distribution in Europe and other growing markets.

But Kerlikowske said the shift does not mean the United States can claim a triumph, as the drug trade threatens to destabilize new regions.

"This does not mark a victory for anyone, and should actually give us pause," he told Reuters in an interview in Colombia late on Tuesday. "The last thing we should do is pat ourselves on the back."

Kerlikowske is promising a bigger emphasis on reducing U.S. drug demand while law enforcement agencies try to clamp down on the new routes.

While the United States is still the world's biggest cocaine consumer, Latin America's cartels have in recent years moved more cocaine to Europe via West African countries such as Guinea Bissau, where drug traffickers have been implicated in the assassination of the president and head of the military.

"For countries that have weakened governmental infrastructures and are more susceptible to corruption, the potential to become a 'narco state' is high," Kerlikowske said.

U.N. officials say the booming West African cocaine trade breeds corruption and threatens security across the region.

"As the world economy recovers, people in business want to make investments in places that are secure. If you look at the antithesis of security, it is drug trafficking and drug addiction," Kerlikowske said during a two-day visit to Colombia, the world's biggest producer of cocaine.

Colombia has received more than $6 billion in U.S. aid over the last nine years, most of it aimed at staunching the flow of drugs and combating cocaine-funded Marxist rebels.

Colombian cocaine output fell sharply last year, although increases in Peru and Bolivia partly made up for the decline.

Latin America's drug wars are largely fueled by U.S. demand and Kerlikowske, a former Seattle police chief, is promising a balanced approach with increased emphasis on drug addiction prevention and treatment programs.

"We want to be helpful not just in interdiction and eradication but across this broad range, as we work hard in our own country to reduce our own demand," he said.