Cabinet officials gathered at the White House complex on Saturday for a drill simulating a smallpox attack against the United States.

The four-hour exercise to test the government's response plans was conducted by Health and Human Services Secretary Mike Leavitt, Agriculture Secretary Mike Johanns and Centers of Disease Control Director Dr. Julie Gerberding and others.

The World Health Organization reported the disease was eradicated in 1980. But there are fears that smallpox could be used by terrorists as a biological weapon.

The United States ended routine childhood vaccination against smallpox in 1971. But the Bush administration, about 15 months after the attacks of the Sept. 11, 2001, ordered some military personnel vaccinated and recommended shots for front-line health care workers.

President Bush, who was spending the weekend at the Camp David presidential retreat in Maryland, did not participate in the exercise at the Eisenhower Executive Office Building next to the White House.

Saturday's simulation was the second drill to check the nation's readiness for catastrophic attacks.

Federal officials said that a similar rehearsal in December for pandemic flu showed that saving lives and containing economic damage would require more planning in local communities and increased production of vaccines and medications.