By Sarah Rainsford
BBC Moscow correspondent
The head of the UN drugs agency says he is extremely concerned about illicit drug cultivation in Afghanistan.
The report says the drug culture is now ingrained in the Afghan society
Antonio Maria Costa was speaking in Moscow, where he was presenting the 2004 UN World Drug Report.
The report says global production of opium remains steady, but is becoming increasingly concentrated in Afghanistan.
However, Mr Costa said the war on terror had given the struggle against drugs trafficking renewed momentum.
The annual UN report shows that Afghanistan is now producing 75% of the world's illegal supplies of opium.
The survey also shows a continuing decline in poppy cultivation in south-east Asia, but production in Afghanistan has increased to fill the gap.
Mr Costa told the BBC that inducing Afghan farmers to grow legal crops is actually the simplest part of the problem to address.
"The big concern we have in Afghanistan is the drug economy," he said.
"All this is becoming profoundly more and more ingrained in the Afghanistan society, and to eradicate the culture of quick money made by illicit cultivation and illicit trafficking is going to be much more difficult than just simply eradicating fields."
But Mr Costa said that increased awareness of the ties between drug money and terrorism had forced many countries to tighten controls.
According to the UN, that has contributed in turn to an overall slowdown in the global spread of narcotics.
But the UN drugs chief called for a crackdown on corruption too, saying that was helping the traffickers.
Mr Costa said current levels of drug abuse remained unacceptably high and he called on governments to step up their efforts against what he referred to as the evil of drugs.