Marine Corps Gen. Peter Pace, vice chairman of the Joint Chiefs of Staff, said more reservists could be called upon if other countries do not soon pledge thousands more troops to form a third multinational division in Iraq.
"We need to be making decisions about alerting reservists over the next four to six weeks," he said. "I would think that by around the end of October or the beginning of November we should be alerting those forces that may need to be called up to relieve or be prepared to relieve (troops there now) if we don't have specificity by then on a third" multinational division.
He said the Guard and Reserve troops should be notified about four months before they would need to ship out because they require some training time.
In other developments:
When it announced a troop rotation plan in July, the Pentagon assumed that it would have available a third multinational division of 10,000 to 15,000 troops to replace the Army's 101st Airborne Division early next year.
Britain is leading one multinational division and Poland is leading another. Among nations mentioned as possibilities for a third division are Turkey, Pakistan, India and South Korea, but none has agreed to do so.
Pace said U.S. Central Command, which is running the military operation in Iraq, may determine that it can find enough active-duty troops to fill any gap next year. But he indicated that mobilizing more National Guard and Reserve troops was an option under active consideration.
"The entire population of the active force of the Marine Corps and the reserve force of the Marine Corps, and the Army and the National Guard and Reserves will be looked at" for possible duty, Pace said in an interview with a group of reporters at a Washington hotel.
There are now about 130,000 U.S. troops in Iraq, including several thousand Guard and Reserve forces. Current plans call for mobilizing two National Guard brigades for duty in Iraq this fall. The Pentagon had hoped that it would need to activate no National Guard units beyond that, but Pace said more could be alerted within weeks for possible deployment.
"What is not clear now…is whether or not what we thought two months ago about the security environment (in Iraq) is still a valid projection, and then whether the coalition countries will or will not come up with a third division," he said.
"There are many countries out there talking about it, and we have every hope that that will happen," he said, "but hope is not a plan."
CBS News National Security Correspondent David Martin reports the call-up, were it ordered, would involve the equivalent of two National Guard and Reserve divisions.