Vienna (AFP) - A UN's anti-drug body added carfentanil, a synthetic substance estimated to be thousands of times more potent than morphine, to its list of controlled substances on Wednesday.
The US had been pushing for the move, and welcomed the decision the UN's Commission on Narcotic Drugs' (CND) unanimous vote.
Carfentanil is one of the substances the United States is trying to crack down on to combat its opioid epidemic, which health officials warned earlier this month was accelerating.
The CND's decision follows the scheduling of a similar drug, fentanyl, last year.
By scheduling substances, the CND requires countries to regulate their production, sale and export.
US officials say that the decision to schedule fentanyl has helped them to better cooperate with other countries to combat the trade over the past year.
An estimated 2.4 million Americans are addicted to opiates, the narcotics that include prescription painkillers, as well as heroin.
Last year President Donald Trump declared the opioid crisis a national public health emergency.
Deaths from opioid overdoses have also been recorded in Canada, Europe, Australia and North Africa.