Developing countries could face a "health disaster" if wealthy countries fail to control drugs, the United Nations Office on Drugs and Crime warned on Monday.
"The developing world lacks the treatment facilities and law enforcement to control drugs," UNODC chief Antonio Maria Costas told a meeting in the Austrian capital.
"This seems to have been forgotten by people in rich countries calling for loosening of drug controls," Costas said.
"Why condemn the Third World, already ravaged by so many tragedies, to the neo-colonialism of drug dependence?"
The UNODC chief identified the increasing use of heroin in East Africa, cocaine in West Africa, and synthetic drugs in the Middle East and South East Asia as warning signs.
Drug addiction, Costas said, was a treatable condition. However, inequality "within and between states marginalises poor people who lack access to treatment".
Chairing the meeting, Iran's envoy to the UN organisations in Vienna, Ali Asghar Soltanieh, described drugs as "a kind of weapon of mass destruction. It's a threat destroying the foundation of families."
In order to combat drug trafficking in Afghanistan, the world's largest producer of opium, "it's not only the countries in the region -- Iran, Afghanistan and Pakistan -- but all countries involved in the region, directly or indirectly, (which) have to come together and work together", Soltanieh said.
At the same time, the UNODC was working with the World Health Organization to achieve universal access to drug treatment and with UNAIDS to prevent the spread of HIV among injecting addicts, he said.
It was also up to rich countries to "unleash the capacity of drugs to do good", Costas said.
"The medical use of narcotic drugs continues to be indispensable for the relief of pain and suffering," he said.
Member states should "overcome cultural and socio-economic factors that deny a Nigerian suffering from AIDS or a Mexican cancer patient the morphine offered to Italian or American counterparts".