Washington.– US President Barack Obama declared the swine flu outbreak a national emergency, giving his health chief the power to let hospitals move emergency rooms offsite to speed treatment and protect noninfected patients.

The declaration, signed Friday night and announced Saturday, comes with the disease more prevalent than ever in the country and production delays undercutting the government's initial, optimistic estimates that as many as 120 million doses of the vaccine could be available by mid-October.

Health authorities say more than 1,000 people in the United States, including almost 100 children, have died from the strain of flu known as H1N1, and 46 states have widespread flu activity. So far only 11 million doses have gone out to health departments, doctor's offices and other providers, according to the Centers for Disease Control and Prevention officials.

Administration officials said the declaration was a pre-emptive move designed to make decisions easier when they need to be made. Officials said the move was not in response to any single development.

Health and Human Services Secretary Kathleen Sebelius now has authority to bypass federal rules when opening alternative care sites, such as offsite hospital centers at schools or community centers if hospitals seek permission.