Rumsfeld said in a broadcast interview that if the United States had able to get its 4th Infantry Division into northern Iraq through Turkey, more of Saddam's Baathist regime would have been captured or killed, diminishing the insurgency.
U.S. forces had to enter Iraq from the south, so by the time Baghdad was taken, much of Saddam's military and intelligence services had dissipated into the northern cities, Rumsfeld said. "They're still, in a number of instances, still active," he said.
In other developments:
As Iraqi security forces develop, Rumsfeld said, they will take increasing responsibility and the insurgency will diminish over time. He estimated current Iraqi security forces at over 145,000.
U.S. forces in Iraq are being reduced from 153,000 to 137,000 or 140,000, Rumsfeld said, although it's possible more security will have to be put into place when new elections take place next year.
Rumsfeld said that at least 30 projects are under way to reduce stress on U.S. forces. For example, he said, a new national security personnel system allows for the use of fewer military people in civilian positions, and the Pentagon is rebalancing the active force with the reserve component.
"So far, we've only used in Iraq and Afghanistan something like 40 percent of the Guard and Reserve," he said. "It's not like everything's been used up."
Rumsfeld defended his "old Europe" characterization of nations such as France and Germany that opposed U.S. policy in Iraq.
"That's not haunting me," he said. "I don't think it was a stunning comment, and it certainly wasn't in any way denigrating anything."