It would be to persuade other nations that it's in their best interests for Iraq to succeed as a stable country, that we are not intent on keeping a permanent presence there, that we will not use Iraq as a springboard to attack them next, that we will work with them to support stability and maintain peace.
It's a bargain that says, "Here's what's in it for you, here's what we're willing to do to help, if you'll in turn do xyz." Certainly there's a chance that may fail, but it doesn't make sense that other nations would say, "Okay, we'll keep up our part of the deal, but you don't have to keep up your part of it."

(edited for typo!

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