"While Iran has shown more support for Shiites. Syria has allowed almost any insurgent group to pass through Syria, but most of these groups have been Sunni," Cordesman said. "Syria has historically tried to manipulate the situation and play more of a spoiler role than anything else."
"In general what the rest of the Arab states [Jordan, Lebanon, etc.] have done collectively is to support unity to try to hold the country together to oppose division between Sunni/Shiite because if these divisions occur in Iraq, they could spread throughout the region," Cordesman said.
Ten countries have sent more than 1,000 troops to the Iraq war since its start in 2003.
Those with troops still in Iraq are: The United States (250,000, with 145,000 remaining); United Kingdom (45,000, with 7,200 remaining with likely withdrawal in 2007); South Korea (3,300 with 2,600 remaining); Poland (2,400, plans to withdraw in December); and, Australia (2,000, with 1,400 remaining).
The following have withdrawn their troops: Italy (1,800 troops); Ukraine (1,650 troops); Netherlands (1,345 troops); and, Spain (1,300 troops).
"If this was a sudden withdrawal, we would remove the one stabilizing force in the country," Cordesman said. "All of the factions would use violence to achieve their own interest -- whether the result would be the emergence of a strongman or unification of the country, or civil war -- we don't know. But we have to remember that there are 27 million people in this country, and in many ways our invasion gives them some responsibility for their fate."
Without foreign help, it is unlikely the United States would have much hope at establishing a stable Iraqi government and rebuilding Iraq's economy.
Economic, political, diplomatic and security forces all have to develop simultaneously in order to start creating a stable Iraq.
"If that all happens at a reasonable pace, the need for external forces will go down and the U.S. can approach a condition where they can reduce their forces," Nash said. "But none of those things have happened in the last 3.5 years -- so it's going to be tough."
"There's no question that the situation is getting worse," Cordesman said. "It's recognized by the command inside Iraq. There's been more than a twelvefold increase between January and October in sectarian violence. It's a clear trend towards an uncontrolled civil war."
While recognizing the deteriorating situation, there are some who still hold out hope for a better Iraq.
"I think the situation is getting worse," Salbi said. "But I think there is still hope in Iraq. We are seeing a lot of elements of hope and progress in southern [and] northern areas of the country, but Baghdad is getting worse."
"I have no reason to think we're going to have a straight line to goodness," Nash said. "But I think the vast majority of problems in Iraq lie in our footsteps, lie at our feet."
The panel of experts include Zainab Salbi, the founder and president of Women for Women International; and, ABC News consultants Fawaz Gerges, retired Maj. Gen. William Nash, Tony Cordesman, and retired Gen. Jack Keane.