Vienna - Bolivian President Evo Morales on Wednesday chewed a coca leaf at a United Nations drug conference in Vienna, underscoring his view that the plant should not be on the UN list of narcotic substances.

Morales was speaking at a conference of the UN Commission on Narcotic Drugs, which is expected to adopt an action plan Thursday to tackle the global drug problem in the coming decade, against the backdrop of limited progress over the last 10 years.

"It's not a drug, it's a medicine," the president said, holding up a coca leaf, which he put into his mouth minutes later.

The leaves should be removed from the international list of narcotic substances, while forms of cocaine should be included instead, Morales told reporters.

Under the UN Single Convention on Narcotic Drugs, coca leaf chewing should have been banned by 1989 in all countries.

While Bolivia would continue to limit coca plant farming, Morales also said that the traditional plant "represents the culture of peoples in the Andean region" and has been used for 5,000 years, to treat ailments such as altitude sickness.

Bolivia's president, who comes from an indigenous family, drew comparisons between himself and Barack Obama, the first black president of the United States, expressing hope that Obama would help decriminalize the coca leaf and would help end the zero-production policy.

The action plan to be adopted in Vienna calls on countries to find a better balance between measures to curb supply and demand, for example by strengthening health care services.

UN goals adopted in 1998 to significantly reduce drug supply and demand by 2008 "have been attained only to a limited extent," the draft of the action plan said.

Taking a larger view of history, the head of the UN Office on Drugs and Crimes (UNODC) noted Wednesday that there had been large improvements since 1909, when he first international conference to control drugs met in Shanghai.

Since then opium production has fallen by 75 per cent, UNODC Executive Director Antonio Maria Costa said.

On Tuesday, the European Commission issued a report that painted a bleak picture of global drug policy, saying it had "no more than a marginal positive influence" in the past decade, as drug prices fell and opium production grew.

One of the sticking points regarding the action plan is whether to include measures for so-called harm reduction, such as providing substitution drugs or needles to addicts. While non-governmental groups support the concept, most UN members are opposed, diplomats said. (dpa)