As American forces closed in on Baghdad last year, senior members of Saddam Hussein's government devised a plan to send suicide bombers in vehicles packed with devastating high-energy explosives that were under UN safeguards.
The disappearance of the explosive, known as HMX (high melting explosives), in mysterious circumstances at the end of the war caused a few nasty moments for President George Bush's presidential election campaign last month.
A letter to Saddam from Dr Naji Sabri, the Iraqi Foreign Minister, five days before the fall of Baghdad, suggests taking the HMX from underground bunkers, where it had been kept under seal by the International Atomic Energy Agency, and giving it to suicide bombers.
He wrote: "It is possible to increase the explosive power of the suicide-driven cars by using the highly explosive material [HMX] which is sealed by the International Atomic Energy Agency [IAEA] and stored in the warehouses of the Military Industry Departments."
The Iraqi regime took credit for several suicide bombs towards the end of the war. After the fall of Saddam, one of the worst attacks - which killed 22 UN workers and the special envoy, Sergio Vieira de Mello, in August 2003 - had an explosive force that could only have come from military grade explosives.
The disappearance of 350 tons of explosives, including 191 tons of HMX, at the time of the war in April last year became a crucial issue in the last weeks of the US presidential election campaign. John Kerry portrayed the failure to secure the explosives, which could have been used to kill US soldiers, as a symbol of Mr Bush's incompetence in Iraq.
It now appears that senior officials in the Iraqi government were discussing the removal of the HMX before the fall of Saddam. The letter from Dr Sabri, obtained by The Independent, was sent on 4 April 2003 as US tanks were advancing on Baghdad. It said that the world was getting the impression that Iraqi civilians were co-operating with American soldiers.
Dr Sabri suggested that the best way of preventing US troops getting too close to Iraqi civilians was "to target their vehicle checkpoints with suicide operations by civilian vehicles in order to make the savage Americans realise that their contact with Iraqi civilians is as dangerous as facing them on the battlefield".
In the last weeks of the US presidential campaign, the Iraqi interim government told the IAEA that the explosives had disappeared from the Al-Qaqaa facility south of Baghdad. The materials were believed to have disappeared after the fall of Baghdad on 9 April because of the failure of US troops to secure them.
The mystery of what happened to the explosives may now be partly resolved by Dr Sabri's letter. Because of the special nature of the explosives, the IAEA had placed them under seal in storage bunkers before the war.
The foreign ministry would have known what was stored there because it dealt with the IAEA and its monitors. There is no proof that the Iraqi presidency acted on the suggestion but there were a number of suicide bomb attacks on US checkpoints at the time. American soldiers now open fire on any car coming towards them that they deem suspicious. Many civilians have been killed.
The letter was given to The Independent by Hoshyar Zebari, the Iraqi Foreign Minister, in Baghdad yesterday. He said it was found in the ministry's archives. There is no reason to doubt its authenticity. The interim Iraqi government may have known about it for some time but was nervous about releasing it at a moment when it might be accused of intervening in the US presidential election.
The letter, marked "confidential and immediate", was sent to Saddam's all-powerful secretary, Abed Hamoud.
Advice on making an unconventional military attack might have been expected from the security services. But it may have been that Dr Sabri, unsure about how long the war would last, wanted to show his his loyalty to Saddam. He fled Iraq and lives in Doha, the Qatari capital.