The sending of anthrax through the mail is an act of terrorism, Bush administration officials said Sunday, without drawing links between the anthrax cases in Florida and New York and the terrorist attacks of last month. 

"It certainly is an act of terrorism to send anthrax through the mail," said Health and Human Services Secretary Tommy Thompson on Fox News Sunday. 

"We should consider this potential that it is linked" to Usama bin Laden, Attorney General John Ashcroft said on NBC's Meet the Press. But, he added, "it is premature at this time to decide whether there is a direct link." Bin Laden is thought to be behind the Sept. 11 attacks. 

Speaking to a convention of anesthesiologists in New Orleans, President Bush pledged to lead the country through "one of the darkest moments in our history." 

"During the past few days, our nation has experienced one of the darkest moments in our history," he said. "Yet even in the midst of this tragedy, the eternal lights of America's goodness and greatness have shown through." 

One man died and at least four others were exposed to the non-contagious bacterium in Florida and New York. In each case, the exposures were linked to mysterious letters containing white powder sent two to three weeks earlier. 

"There are a lot of people in America that are afraid, and understandably so, because bioterrorism has never hit America before, and people are afraid ... of the unknown," Thompson said. "They don't know about anthrax." 

Thompson said there are more than 2 millions doses to treat 2 million people for 60 days for exposure to anthrax, and thousands of medical professionals are on alert, Thompson said. He also said the administration will ask Congress this week for $1 billion to increase the amount of purchases for the medical supplies. 

Sohail Shaheen, a spokesman at the Taliban's embassy in Islamabad, Pakistan, told Meet the Press that by focusing only on bin Laden, U.S. officials "have freed all other terrorists organizations to do what they can do. ... America has many enemies, open and secret. They should not focus only on Usama. ... Then the real culprit will escape and there will be more incidents like this under the name of Usama." 

Ashcroft pointed out that bin Laden's Al Qaeda network has been threatening the U.S., warning of a new "storm of airplanes" and advising Muslims in the United States and Britain to avoid flying and to stay away from tall buildings. The FBI on Thursday said it had received information there might be additional terrorist attacks inside the United States or abroad in the coming days. 

Yet, not wanting to further worry a nation already on edge, Ashcroft also downplayed the threats. 

"We've been getting messages that are more propaganda than anything else," said Ashcroft, who followed the Taliban representative on NBC. 

"I don't think it's valuable for us to deal with propaganda," Ashcroft said. "I don't want to further their position or enhance their standing. I think the American people can evaluate the credibility of it and evaluate it for what it is."  

The Associated Press contributed to this report