Iraq buys $5 bn in US arms

Iraq will buy $5 billion on US weapons, military equipment and training.

That's one reason why the US wants to dominate the Middle East and is related to control over oil resources: if friendly regimes are put in power where there's a lot of oil, then the oil revenues (petrodollars) will be invested in the US/Western countries, either in the form of weapons purchases or investment. Those maintain the close relationship between the US and friendly governments in the Middle East.

So that's one reason why the US invaded Iraq because of oil.