JOHN ROBERTS, CNN ANCHOR, THIS WEEK AT WAR: President Bush and Iraq's prime minister, was it anything more than just a grand photo op? Will it have any effect on the situation on the ground in Iraq?

The Iraq study group says, pull out the troops. President Bush says, no, hell, no, in fact. And as the world wrestles over words to describe the violence in Iraq, we'll take a look at just what makes up a civil war. I'm John Roberts with THIS WEEK AT WAR. Let's take a look at what our correspondents reported day by day this week.

Monday the week begins with more bloody sectarian violence. Baghdad authorities find 36 bodies plus four people killed in car bombings. Tuesday, in Turkey, Pope Benedict XVI offers an olive branch to Muslims he angered with comments about Islam and violence talking of, quote, mutual respect. Wednesday a leaked memo from the national security adviser portrays Iraqi Prime Minister Nuri al Maliki as either ignorant, lying or weak. Thursday, President Bush stands with al Maliki and pledges again to stay in Iraq to get the job done. Friday, Hezbollah turns out thousands of protesters in the streets of Beirut, determined to bring down Lebanon's pro-western government...

And also in New York, Nir Rosen, he is a fellow of the New America Foundation, also the author of "In the Belly of the Green Bird, the Triumph of the Martyrs in Iraq..."

ROBERTS: Nir Rosen, you spent an awful lot of time in Iraq and in the region. Is that the way you see it, that the sectarian violence in Iraq now has reached critical mass, so that it is self- sustaining, it no longer needs any more sparks from the outside, al Qaeda doesn't need to blow up any more mosques to keep this going?

NIR ROSEN, NEW AMERICA FOUNDATION: Yes, that's correct. There's been a civil war in Iraq I would said from June 2004 when there was a hand-over, or an alleged hand-over from sovereignty. And the Shia-led government has been going after Sunnis.

The second battle of Fallujah, Shias didn't really help the Sunni fighters and Sunni refugees poured into western Baghdad and began displacing Shias and a process began of sort of ethnic cleansing very similar to Bosnia.

I don't think there was ever a significant foreign role to this. I think this was something sort of inevitable when you destroyed the regime and left a vacuum and put in power various militias who are competing for power...

ROBERTS: Nir Rosen, Iraq is the nexus of the region, really on the fault line between Sunnis and Shiites. What's the potential impact for the rest of the region if Iraq continues to melt down?

ROSEN: Well, Jordan and Saudi Arabia are especially in a panic about this new aggressive Shia dominated Iraq. And I think you're going to see as the Shias basically push all of the Sunnis out of Baghdad which is inevitable greater Saudi and Jordanian involvement supporting Sunni militias.

I think the nation state won't matter. Borders won't matter. And you're going to see a regional civil war, something like the Great Lakes War in Africa involving several different countries, hundreds of thousands dead, millions of refugees. You already have a couple of million Iraqi refugees and those numbers are growing...

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