David Johnson, the U.S. assistant secretary of state for International narcotics and law enforcement, said narcotics was a "very challenging situation" for the international community.
In a Washington briefing to reporters, Johnson said controlling production and consumption requires a holistic approach from the international community.
"It illustrates also that consumption of drugs is an international phenomenon," he said.
Washington links the illicit drug trade to terrorist activity, noting the Taliban in Afghanistan are funded in part by the opium trade. The U.S. Treasury Department in 2006 listed Sobhi Fayad, a Hezbollah official, as a Specially Designated Terrorist due to connections to the drug trade and the counterfeiting of U.S. dollars.
"The country regrettably with the highest usage is Iran, which has substantial efforts under way to help deter this," he added.
Iran embarked on a unilateral effort to control drug trafficking along its border, noting several members of its security forces were killed during counter-narcotic operations.
"So, it's a global problem and one that we work on globally with our partners," said Johnson.