In 1980 Saddam was invited by the Saudis to visit, and he was then encouraged to attack Iran -- it is claimed that the Saudis assured Saddam of Carter's backing. Once Reagan came into office of course the US quite overtly started backing Saddam, starting by removing his regime from the US list of Terrorist Nations, thus opening the way for the US to provide financing, arms and assistance as well as technology.

It should be remembered that Saddam was a former CIA thug. http://www.upi.com/Business_News/Security-Industry/2003/04/10/Exclusive-Saddam-key-in-early-CIA-plot/65571050017416/