While American forces invading Iraq face the threat of chemical attack, they could themselves be using biochemical agents which are banned under international law.
The US Secretary of Defence, Donald Rumsfeld, revealed earlier this month that American forces are planning to use "non-lethal" biochemical weapons such as anti-riot gases and crowd control agents if they invade Iraq. Mr Rumsfeld and General Richard Myers, chairman of the US Joint Chiefs of Staff, told the House of Representatives Armed Services Committee they were preparing to ask President George Bush for permission to use these weapons, known in military circles as "calmatives", on Iraqi civilians, in cave systems or to take prisoners.
But two of Britain's leading authorities on chemical weapons, Professor Alistair Hay and Professor Julian Perry-Robinson, who are collaborating on an expert guide for the World Health Organisation, said such weapons are illegal under the 1992 Chemical Weapons Convention and the 1928 Geneva Protocol, which ban the use of chemical agents against people in wartime.
"It would be absolutely outrageous if they did this," said Prof Hay, an epidemiologist at Leeds University. "Surely this war against Iraq is to stop the use of those weapons, not about also using them."
The dangers of such weapons were exposed, the experts said, when Russian special forces used an opiate-based crowd control gas, with devastating consequences, on Chechen rebels holding theatregoers hostage in Moscow in October. Both men said Mr Rumsfeld's comments also threatened to put the Pentagon on a collision course with Britain.
Ministry of Defence experts have repeatedly warned their US counterparts that their proposed use of these weapons in warfare is illegal.