Although Saddam became the president of Iraq in 1979 he was the power in the land long before that.
The USA was a very important supporter of Iraq on his march to become a regional power.
And of course one reason was that they wanted to use him and Iraq to counter the threat of Iran.

Here is what Said K Aburish had to say [or write] in his book "Saddam Hussein" published in 2000.
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"All warnings aside ,in 1989 the United States supplied Iraq with helicopter engines,vacuum pumps for a nuclear plant,sophisticated communications,computers,bacteria strains, and hundreds of tonnes of unrefined sarin.
Furthermore the pro Iraq activities of the US -Iraqi Business Forum ,led as it was by former diplomats with solid connections with the State Department , were augmented by the work of Kissinger Associates , the consulting firm headed by former secretary of Sate Henry Kissinger .
Representing companies such as Volvo,Fiat and Hunt Oil ,this firm took their signal from the government .Two of the insiders Brent Scowfield and Lawrence Eagleburger , were to join the Bush administration in the spring of 1989 , the former as National Security Adviser."
albert