In comments that will be seen as criticising President Obama's decision to pull out of Iraq in 2011, General Petraeus said: “[During the 2006 surge] we had to show that we were indeed the biggest tribe in town and secure people. Then they were willing to take on the murderous individuals who were making life so difficult."
“The fabric of that society, which we had worked hard with our Iraqi partners to bring back together - to get a few stitches back into that society through reconciliation, broke down. Unfortunately that architecture, those agreements and initiatives, have been undermined by sectarian actions.”
On the question of US or British intervention in the current conflict, he added: “There has to be a huge idea here, and it has to be that if there is to be support for Iraq it has to be support for a government of Iraq - a government for the people and responsible to Iraq’s institutions.
“This cannot be the US being the airforce for Shia militias in a Shia on Sunni Arabs fight. It has to be a fight for all of Iraq against extremists who are wreaking havoc on a country that had an enormous opportunity back in 2011.
“If america is to offer support, it has to be in support of a government rather than one side in a sectarian conflict.”
He made his comments as former prime minister of Australia John Howard hinted that the West should be doing more to combat the Isis insurgency.
"The West needs to recover its cultural self belief,” he said.
"It needs to understand that the values we all instinctively think about - for all their flaws and blemishes - have been incredibly successful and have been responsible for repulsing assaults on liberty.
"It remains my view that Islamic extremism is a far greater threat than many people believe.”
He added of President Obama's approach to the threat of Islamic fundamentalism: "We have an incredibly chaotic situation in Iraq and we worry about Afghanistan. I think he has an altogether too complacent analysis of the threat posed."