Many of those who advocate for an early withdrawal from Iraq argue that Iran can be persuaded to play a constructive role there. But all of Iran’s actions suggest that it wishes to keep peace from breaking out in its neighbouring state. As General Petraeus told the BBC
“The rockets that were launched at the Green Zone yesterday, for example... were Iranian-provided, Iranian-made rockets," he said, adding that the groups that fired them were funded and trained by the Quds Force.
"All of this in complete violation of promises made by President Ahmadinejad and the other most senior Iranian leaders to their Iraqi counterparts."
Iran is a state with hegemonic ambitions that is happy to use terrorist proxies to achieve its aims. A premature withdrawal from Iraq would be an invitation to it to expand its sphere of influence.