TRIESTE, Italy (Reuters) - Iran is committed to a regional effort to tackle drug trafficking from Afghanistan and has begun joint counter-narcotics operations with Afghan and Pakistani authorities, a senior United Nations official said. Iran, which has seen demonstrations after contested presidential elections earlier this month, declined an invitation to an international conference hosted by Italy on Saturday aimed at promoting stability in Afghanistan. But Antonio Maria Costa, head of the United Nations Office of Drugs and Crime, said Tehran was taking steps to tackle the flow of heroin from its eastern neighbour, which has left Iran with the highest rate of drug addiction in the world. Most certainly the Iranian government is strongly committed to a regional effort, he told Reuters in an interview. In recent weeks, we have seen tripartite drug interception. This is very new, it has not happened in the past. Afghanistan, immersed in conflict since the 2001 invasion to topple the Taliban, produces more than 90pc of the worlds supply of opium, a thick paste from poppy that is then processed to make heroin and smuggled abroad. Costa said two important drug stings had taken place in recent weeks based on information supplied by the three countries, and another was due within the next fortnight. All of this seems to be a good omen in political terms because in the past some of these countries have been at odds with one another and being able to operate together means that they have overcome past political differences, he said. The presidents of the three neighbouring states - Pakistan, Iran and Afghanistan - held talks in May in Tehran aimed at deepening cooperation. They have established an anti-narcotics planning office in Tehran and six offices along their border, three in each country. Costa called Afghanistans US-backed efforts at drug eradication a sad joke, noting that only 6,000 hectares of opium production would be destroyed this year just 3 per cent of the total. He welcomed a US change in strategy away from eradication and towards supplying hundreds of millions of dollars in agricultural aid to provide farmers with alternative crops. We need the countries at this meeting and the development institutions to display in Afghanistan an economic power as forceful as Nato military firepower, Costa said. Roughly two-third of Afghanistans crop is produced in the fertile southern province of Helmand, bordering Pakistan, where British troops are being reinforced by 10,000 US Marines. Costa said he hoped the military surge would help shut tight the border to flows of illegal arms, fighters and drugs.