New Delhi: The United States helped Iraqi tyrant Saddam Hussein attack Iran with chemical weapons in the 1980s during the Iran-Iraq war, it has been claimed. Ronald Regan's administration, which supported the Iraqi dictator, toppled two decades later by the Bush government, fed information to Baghdad that helped them launch strikes. A generation ago, America's military and intelligence communities knew about and did nothing to stop a series of nerve gas attacks far more devastating than anything Syria has seen. Iraq used mustard gas and sarin in early 1988 in four major offensives which helped bring about the end of the eight-year conflict. During the whole war, up to 20,000 Iranian troops were killed by mustard gas and nerve agents from Iraq and 100,000 were wounded. But they were also the last in a series of chemical strikes stretching back several years that the Reagan administration knew about and didn't disclose. US officials have long denied acquiescing to Iraqi chemical attacks, insisting that Hussein's government never announced he was going to use the weapons. But retired Air Force Col. Rick Francona, who was a military attaché in Baghdad during the 1988 strike said, "The Iraqis never told us that they intended to use nerve gas. They didn't have to. We already knew.” According to recently declassified CIA documents the US had firm evidence of Iraqi chemical attacks beginning in 1983. At the time, Iran was publicly alleging that illegal chemical attacks were carried out on its forces, and was building a case to present to the United Nations. But it lacked the evidence implicating Iraq, much of which was contained in top secret reports and memoranda sent to the most senior intelligence officials in the US government. The Reagan administration decided that it was better to let the attacks continue if they might turn the tide of the war. And even if they were discovered, the CIA wagered that international outrage and condemnation would be muted. It has been previously reported that the United States provided tactical intelligence to Iraq at the same time that officials suspected Hussein would use chemical weapons. But the CIA documents, which sat almost entirely unnoticed in a trove of declassified material at the National Archives in College Park, Md., combined with exclusive interviews with former intelligence officials, reveal new details about the depth of the United States' knowledge of how and when Iraq employed the deadly agents. They show that senior US officials were being regularly informed about the scale of the nerve gas attacks. They are tantamount to an official American admission of complicity in some of the most gruesome chemical weapons attacks ever launched.