Since the September 11th terrorist attacks, U.S. officials have warned that the next plot to kill large numbers of Americans could involve deadly biological agents.

Homeland Security Secretary Tom Ridge told reporters that federal agencies are hard at work combating the potential threat.

"The president [Bush] has put forward a new initiative that will fully integrate our current bioterrorism efforts across public health, medical, law enforcement, intelligence, and homeland security community," he said. "From the creation of a biological attack warning system, to an improved distribution system of critical antibiotics and vaccines, this plan charts a course towards our goal of a strong and robust bioterrorism defense."

The initiative, titled "Bio-defense for the 21st Century" includes boosting research into biological threats, expanding a network of sensors that continuously monitor air particles for potential chemical and biological agents in major metropolitan areas and increasing America's capacity to respond to a catastrophe.

"Our public health system has to be prepared in order to deal with widespread illness and casualties in the event of a biological attack," said Health and Human Services Secretary Tommy Thompson.

That means readying emergency response teams and stockpiling medical supplies, which Mr. Thompson said is already being done.

"These stockpiles include large quantities of antibiotics, chemical antidotes, anti-toxins, life-support medications and many other surgical items," he added. "We call these 'Push Packages' and they are stationed in strategically located, secured warehouses ready for immediate deployment."

Secretary Thompson added that The United States now has enough smallpox vaccine to inoculate every person in the country, if necessary.

Deputy Defense Secretary Paul Wolfowitz said no one should underestimate the threat of bioterrorism, which could exact a death toll far greater than the attacks of September 11, 2001.

"The American people must appreciate the magnitude of the danger that we face from possible biological terrorism," he said. "The threat is real. It is deadly serious. As horrible as it was to have thousands of innocent Americans killed on our own territory killed on that tragic day [September 11th], that is nothing compared to what terrorists could do with the biological weapons that we know they have been actively seeking. A mass-attack with anthrax or some other biological agent could bring about civilian casualties and catastrophic damage to our economy on a scale far beyond what we experienced on September 11th, as devastating as that was."