"I have no question, the intelligence community has no question, that the factory was used to manufacture a chemical used in making nerve gas," the National Security Adviser, Sandy Berger, said.
The chemical - an ethyl-methyl-phosphorus compound, according to Newsweek magazine - has no use in the production of pharmaceuticals, reports said. The US would not say how it had obtained samples of the chemical, citing security concerns.
Berger said: "We have physical evidence of that fact, but we are not going to release it."
The Sudanese government and the staff at the factory have protested that it was a factory making drugs for use in Sudan and for export, including anti-malaria, anti-parasite and other treatments. It had a contract to produce medicines for export to Iraq.
Since the US has refused to discuss its evidence, and Sudan has been willing to allow journalists to explore the factory's remains, there is suspicion that the US made a mistake, or deliberately attacked a civilian facility.
Sudan has protested to the United Nations, and wants an independent team to visit the site to verify that it was not a chemical weapons plant.
The United States last night bluntly told the Security Council it would have no business launching an investigation of its missile attack.
Ambassador Peter Burleigh said after a brief meeting of the Council in New York: "Putting together a technical team to confirm something that we already know would seem to have very little point to us."
Sudan had suggested that "a neutral respected person like ex-president Carter" could lead an investigation team.
A report in the Arabic press last year suggested that Ayman al-Zawahiri, a leader of Egyptian Islamic Jihad, met Sudan's Islamic leader, Hasan al-Tourabi, regarding the plant.
They decided to find new financing to develop its chemical and bacterial weapons-producing facilities. US reports suggested the plant had a secure perimeter and was patrolled by Sudanese military.
The US launched cruise-missile attacks on camps in Afghanistan and the factory in Sudan within two weeks of bombings at its embassies in Kenya and Tanzania.
The operation, code-named Infinite Reach, was so secret that even staff within the office of the US Defense Secretary William Cohen were not aware of it, according to Newsweek.
The scale of the damage suffered by the US in the 7 August bombings has also become clearer. The US embassy in Nairobi contained not just a CIA station, but was the key to America's electronic intelligence gathering operation in east Africa, Jane's Intelligence Review reported. It was also the operational control centre for the US Army's Central Command in the region.
At the time of the bombings, the CIA staff based in the embassy were focused on investigating ties between Iraq and Sudan, especially with regard to the dispersal of Iraq's manufacture of weapons of mass destruction, the report said.
Among the dead after the embassy bombing were military personnel, including one who had received training in Arabic before being sent to Nairobi. Reports in Washington said at the time that CIA personnel had been killed in the bombing, and that Nairobi and Dar es Salaam were two of the few remaining CIA stations in sub-Saharan Africa.
The details emerging of the attack suggest the bombing was carefully planned to hit back at the CIA, which has been conducting a covert war against Osama bin Laden for at least 18 months. Bin Laden is accused by the US of organising the two embassy bombing in East Africa. It is reported to have mounted two arrest attempts, one in March this year, the other in the middle of 1997.
If the embassy was indeed hosting all of the intelligence functions ascribed to it, it is the most devastating attack on US intelligence since the Beirut embassy was destroyed in 1983. The information would also help to explain why the US military was so anxious to prevent anyone from entering the embassy after the bombing.
t Britain yesterday responded to demands to expel Islamic "fanatics" by promising new powers in the autumn to tackle terrorist fund-raisers and supporters living in the UK.
Officials said new powers would be proposed for the Home Secretary, Jack Straw, to expel "terrorist" sympathisers using Britain as a haven. John Pilger, Review, page 4Reuse content