Blast Kills 8 at Iraqi Parliament Building

In a report to be issued Friday, military expert Anthony Cordesman concludes that even if the current U.S. troop increase is a success and creates some degree of stability and political unity, the perception of most Iraqis and others in the Middle East and Europe will be that the United States "lost" the war in Iraq.

"It is more than possible that a failed president and a failed administration will preside over a failed war for the second time since Vietnam," Cordesman says in "Iraq's Troubled Future: The Uncertain Way Ahead," to be published by the Center for Strategic and International Studies. He previously advised McCain.

Cordesman also warns that a "security first strategy" is unworkable, particularly when it is local rather than national. "The battle for Baghdad is only a tactic," he says.

Other analysts suggested, however, that the only surprise was that an attack inside a major government installation had not happened more often.

"This is bad news, but they've been trying to secure a large area in the middle of a war zone, and the fact is that it has so far happened rarely," said Michael E. O'Hanlon of the Brookings Institution. "The Green Zone is still the least of our concerns."

Wright reported from Washington. Special correspondents Naseer Nouri and Waleed Saffar in Baghdad and staff researcher Robert E. Thomason in Washington contributed to this report.