By Pam O'Toole BBC regional analyst

The executive director of the UN Office on Drugs and Crime says that the price of Afghan opium has recently risen to around $600 per kilogram, making it more difficult to offer attractive incentives for farmers to grow legal crops.

Antonio Costa was speaking to the BBC in London, where he is holding talks with the UK Government, which is co-ordinating international efforts to stamp out illicit drugs production in Afghanistan.

No agricultural commodity can command a price of $600 per kilo Antonio Costa UNODC

Afghan opium is currently selling for almost twice the price it was this time last year and around 17 times more than the lowest price reached during the 1990s.

The latest price increase is likely to pose an additional challenge to Mr Costa's agency and to Afghan President Hamid Karzai, who imposed a comprehensive ban on drug production and trafficking shortly after taking power a year ago.

No one it seems, can fully explain why the price of Afghan opium has suddenly shot up.

Split profits

Some say it could be because farmers are uncertain about how far Afghanistan's central government will be able to enforce its ban on cultivation.

Mr Costa said there are indications that Afghan farmers have been staggering or delaying planting for this year's harvest, possibly because of a perceived increase in risk.

It was too early to estimate how big the 2003 harvest would be, he said, but his office did not see a significant decline.

Challenge to find viable crops for farmers

Whatever the reason, Mr Costa warned that the price rise presents an additional challenge to those trying to stamp out illicit drugs production.

"There are dangerous connotations. One is the fact that at such very high prices there is very little possibility of offering farmers incentives for alternative licit cultivations - no agricultural commodity can command a price of $600 per kilo," he said.

"Second, such very high prices generate a very high revenue - the revenue is partly kept by the farmer, to some extent is shared with local warlords or provincial governors or local commanders."

Long haul

Last autumn, the UN reported that poppy harvests in Afghanistan had increased 18-fold in 2002 after a dramatic drop the year before following a Taleban ban on production.

Farmers had taken advantage of a power vacuum before the collapse of the Taleban in 2001 to plant the crop.

Mr Costa said that this large harvest, combined with the price rises meant that poppy production in Afghanistan may have generated around $1.2bn in 2002 - far more than in previous years.

It is vital, he said, not only to offer farmers robust incentives to stop illicit planting, but to work with local authorities to ensure that cultivation becomes more risky.

The aim is to stop drugs at their source

Mr Costa added that more work also needed to be done to step up interdiction at borders and strengthen Afghanistan's own law enforcement system.

His agency is expecting to expand a number of initiatives in Afghanistan and neighbouring countries this year.

Nevertheless, Mr Costa says,, he expects it to be a long haul.

Similar drugs eradication programmes in other countries have taken around 10-15 years.

Afghanistan is currently the world's largest producer of illicit opium, accounting for almost three-quarters of global opium production.