If the US wanted Iraqi oil it would ours.
What will happen is the UN and Countries like France Germany China and Japan will come together and support the US/UK rebuilding Iraq to get their foot in the door. The New government of Iraq will have complete control of the oil in Iraq and will decide how to use it.
If US companies get contracts great, but dont imply that is a reason the US is invading Iraq. The US wont force contracts on the new Iraqi government.
We are preparing to open up Alaska, once the situation in Venezuela gets resolved the US wont have any need for Iraqi oil.