The meeting has been postponed to Thursday by North Korea, which did not specify the reasons behind the delay, a spokesperson for the South Korean Unification Ministry.
UK will host the fourth international conference on the illegal wildlife trade, bringing global leaders to London to tackle the strategic challenges of the trade.
The researchers found that states that allow the use of cannabis for medical purposes had 2.21 million fewer daily doses of opioids prescribed per year.
Facebook is currently facing the heat over the leak of personal and other data of some 50 million users to political consulting firm Cambridge Analytica.