Key comments by Ryan Crocker

"There will be no single point at which we can claim victory." "It is possible for the United States to see its goals realised in Iraq." "It is no exaggeration to say Iraq is ... a traumatised society." "Iraqis are facing the most profound political and economic challenges imaginable." "The trajectory of political, economic and diplomatic developments in Iraq is upwards, although the slope of that line is not steep."   "The seeds of reconciliation are being planted."   "Prime Minister Maliki and other Iraqi leaders face enormous obstacles in efforts to govern effectively."

He said: "The army can't sustain the deployment they have now without changing the rotation system.

"So he's looking at having to draw down by next spring. They are overstretched."

Zibakalam Sadegh, a professor of political science at Tehran university, dismissed claims by Crocker that Iran would benefit from continued instability in Iraq.

"Whatever has gone wrong and whenever there are security failures, they keep blaming Iran for that," he told Al Jazeera.

"None of the American leaders have ever been able to answer the simple question of 'what has Iran to gain from insecurity in Iraq?'.

"Indeed, Iran has everything to gain from a stable Iraq."