No decision has been made yet, and the administration of President George W. Bush is still weighing whether to go forward with a smallpox vaccination program and whether to limit it to the military or also include civilians, the officials said.

"The DoD (Department of Defense) position is that we should vaccinate the total force," said an official, who asked not to be identified.

The official cautioned that plans do not call for an immediate vaccination of the entire force, although troops deploying to high-threat areas could be assumed to be first in line.

"It is true that at any time that process could begin, but the final decision has not been made," a second defense official said.

"Eventually, the plan would be the entire force, with first responders and frontline troops being the ones to receive vaccinations first," he said.

The administration has hesitated about undertaking massive inoculation of the civilian population because the smallpox vaccine can lead to complications -- and even death -- in a small percentage of people.

"The fortunate thing is you have a younger population in the military. So we are less at risk," the defense official said.

But mass inoculation programs touch a sensitive nerve for the military.

A campaign to inoculate all US troops against anthrax in the 1990s encountered resistance among some members of the military who were fearful of long-term health effects such as those experienced by veterans of the 1991 Gulf War.