But there are doubts about the safety of the killer fungus they have developed, and the legality of any plan to spray the spores over Afghanistan - the source of most of Europe's poppy opium for heroin.
The UK and the US are funding research on a new biological weapon in an effort to destroy the heroin trade.
The research, by former Soviet scientists in Uzbekistan, is being supervised by the United Nations Drug Control Programme (UNDCP).
But there are doubts about the safety of the killer fungus they have developed, and the legality of any plan to spray the spores over Afghanistan - the source of most of Europe's poppy opium for heroin.
The BBC has obtained unique access to the laboratory across the border from Afghanistan, in Uzbekistan, where the fungus is now being tested.
Huge step
It has filmed in the laboratory and spoken to the scientist in charge, Professor Abdukarimov Abdusattar, as well as to a British scientist in Bristol, Mike Greaves, who oversees the work on behalf of the UNDCP.
Professor Abdusattar says one test tube contains millions of spores - sufficient to destroy 10 square metres of poppies by attacking the roots and killing them from inside.
But moving from research paid for largely by the UK and the US to using what amounts to a biological weapon would be a huge step.
Some scientists are worried the culture could mutate and attack other plants, or harm animals and humans.
Also, spraying the fungus over the poppy fields of Afghanistan without permission from the Taleban regime there, which is unlikely to be granted, could amount to illegal biological warfare.
However, Mr Greaves says the fungus appears so far to be safe.
"We are still working on the safety aspects, to be absolutely sure," he told the BBC's Panorama programme.
"At the moment we have tested, for example, 130 other plant species and it does not affect any of those."
You can see the whole of Panorama's investigation "Britain's secret war on drugs" on BBC One, on Monday at 2200 BST (2100 GMT).