Documents released Monday by the State Department under the Freedom of Information Act shows that Mr. Rumsfeld played an instrumental role in securing the US support for President Saddam Hoseyn during the Iran-Iraq war that lasted from 1980 to 1988, a support that included the export of anthrax, cluster bombs and biological weapons.

Washington sold chemical warfare to Iraq even though the CIA was reporting on a daily basis about Iraq using these weapons against Iranian forces and civilians.

Mr Rumsfeld, in a September interview with CNN, said he "cautioned" the Iraqi leader against using banned weapons, but the claim stands at odd with the declassified documents of his 90 minutes meeting with Mr. Hoseyn.

He has also said that he had nothing to do with helping Iraq in the war against Iran.

Though observers say the documents would embarrass Mr. Rumsfeld, but it is unlikely that it would affect President George W. Bush’s plans to attack Baghdad.

The British newspaper "The Guardian" quoted Rick Francona, an ex-army intelligence lieutenant-colonel who served in the US embassy in Baghdad in 1987 and 1988, as having said: "We believed the Iraqis were using mustard gas all through the war, but that was not as sinister as nerve gas.

"They started using tabun [a nerve gas] as early as 83 or 84, but in a very limited way. They were probably figuring out how to use it. And in 88, they developed sarin", he said, adding that on first of November 1983, the then Secretary of State, George Shultz, was passed intelligence reports of "almost daily use of CW (chemical weapons)" by Iraq.

Howard Teicher, an Iraq specialist in the Reagan White House, testified in a 1995 affidavit that the then CIA director, William Casey, used a Chilean firm, Cardoen, to send cluster bombs to use against Iran's "human wave" attacks.

A 1994 congressional inquiry also found that US companies, under licence from the commerce department, had shipped dozens of biological agents, including various strains of anthrax, to Iraq. In 1988, the Dow Chemical company sold $1.5m-worth of pesticides to Iraq despite suspicions they would be used for chemical warfare.

When Saddam attacked Iran, the United States was a bystander, having no diplomatic relations with either side. But when Iranian troops booted out Iraqi invading forces in 1982, crossed the Shat el Arab river and advanced to a few kilometres of Basra, with Ayatollah Roohollah Khomeini, the leader of the Islamic revolution, determined to push his advances right to the heart of Baghdad, President Ronald Reagan authorised the supply of military intelligence on Iranian forces, stating that Washington would do all it could to prevent Iraq collapsing.

There was no comment on the story of Mr. Rumsfeld's involvement from the officials in Tehran. but Iran always criticises the West's "double standards" and denounces major western nations for providing Iraq with deadly chemical and biological weapons and modern arms to fight Iran.