* Cocaine market shrinking, opium cultivation up - UNODC
* Worldwide drugs demand little changed in recent years
* East and West Africa seen vulnerable to drug trafficking
* Uruguay says "old policies failed" (Adds Uruguay statement, paragraphs 10-11)
By Fredrik Dahl and Derek Brooks
VIENNA, March 13 (Reuters) - The global fight against narcotics has suffered serious setbacks, including record opium cultivation in Afghanistan and a surge of trafficking-related violence in Central America, the U.N. anti-drugs chief said on Thursday.
Yury Fedotov also noted some successes, such as a shrinking cocaine market, at the start of a two-day meeting that will review implementation of a 2009 plan of action to combat the drugs problem before a special session of the U.N. General Assembly in 2016, amid a heated debate on the merits of drugs liberalisation.
Fedotov, executive director of the United Nations Office on Drugs and Crime (UNODC), said reductions in the supply and demand for some drugs in one part of the world had been partly offset by increases elsewhere.
"The overall magnitude of drug demand has not substantially changed at the global level," he told the conference, which organisers said drew 1,500 representatives from member states, civil society organisations and other groups.
"We are strongly concerned about the vulnerability of some regions, notably West Africa and East Africa, to illicit drug trafficking," Fedotov said.
There are around 27 million "problem drug users" in the world and about 210,000 narcotics-related deaths a year, a UNODC document prepared for the conference said.
There is disagreement on how to best counter the problem, with critics questioning the 'war on drugs' and advocating some legalisation to try to undermine criminal gangs that thrive on narcotics trafficking.
In a move that will be closely watched by other nations discussing drug liberalisation, Uruguay's parliament in December approved a bill to legalise and regulate the sale and production of marijuana - the first country to take such a step.
In the United States, Washington and Colorado states have legalised the sale of cannabis under licence, although federal law has not changed.
Uruguay defended its new rules, saying drug trafficking caused more deaths than addiction.
"Eighty were killed last year from drug trafficking but none from the use of marijuana. So what is worse? Drugs or drug trafficking?" said Diego Canepa, vice secretary of the office of President Jose Mujica.
"The old policies have failed," he said. But Uruguay was "not a model for anybody ... this is about our own policies."
Fedotov, who said earlier this week that legalisation was not a solution, told the meeting that dismantling the provisions of three international drug control conventions - one dating back to 1961 - would not help protect people's health.
The head of the International Narcotics Control Board, which monitors compliance with the conventions, said they had helped limit drugs use to medical and scientific purposes.
"Do we have the right to weaken the system that we took more than 100 years to put in place?" Raymond Yans asked.
The International Drug Policy Consortium, a non-government network attending the meeting, said the existing drug control system had worsened stigma, violence and organised crime.
But another group, Drug Policy Futures, said: "The legalisation of alcohol and tobacco have been a global public health disaster - why should we go down the same road by legalising additional addictive drugs?"
Fedotov said the total area under coca bush cultivation fell by 26 percent between 2007 and 2011. Cocaine use in North America, the world's largest market, has fallen sharply, UNODC figures show. International cooperation has also been strengthened, with information-sharing and coordination among law agencies.
"And yet there have been serious setbacks," Fedotov said, noting opium cultivation reached record levels in Afghanistan in 2013. Afghanistan supplies 90 percent of the world's opium, from which heroin is made, and its poppy-driven economy is helping to fuel the 13-year-long war in the country.
Fedotov also said drug trafficking "has triggered a dramatic surge of violence in Central America". (Editing by Alistair Lyon and Robin Pomeroy)