Homeland Security officials say they have improved security throughout the U.S. mass-transit system. But they say there is no way to completely guard against an attack in the United States similar to last week's bombings in London.
Department of Homeland Security Secretary Michael Chertoff told the ABC television program This Week, U.S. authorities can try to minimize the risk of an attack on American soil, but cannot prevent it entirely.
"There is no perfect security in life, but we are constantly raising the baseline of our security and we're making sure that we're using a multiple-faceted approach, in terms of our tactics and our layers of protection," he said.
His comments were echoed by White House Homeland Security Adviser Fran Townsend, who emphasized that American public transportation systems are safer than before the terrorist attacks in the United States on September 11, 2001. She appeared on Fox News Sunday.
"We put extensive warnings about the kind of techniques al-Qaida uses to do these attacks at the state and local level, so they can take protective measures. It is a lot safer. We look every day, Brit [Hume]," she said, "to make it safe. But there are no guarantees in this world. I could have gotten hit by a bus coming in here. But we are working hard to ensure the safety as best we can."
Ms. Townsend said that is the purpose of U.S.-led wars in Iraq and Afghanistan is to fight terrorists overseas, before they strike in the United States.
But on NBC's Meet the Press, Stephen Flynn, author of a book on U.S. government efforts to fight terrorism, disputed this line of reasoning.
"We have spent about $500 million a year, total, on transit security in the United States, since 9/11, almost four years," said Mr. Flynn. "We are spending that every three days in the war on Iraq. We still have virtually all our eggs in the basket of taking the battle to the enemy, as if the enemy was all concentrated in those two countries, instead of that we are dealing with an ongoing threat that is truly global."
Meanwhile, the Homeland Security Secretary said U.S. authorities have been constantly monitoring so-called terrorist chatter. He said U.S. officials gathered what he termed "general strategic intelligence," but did not anticipate the London bombings.
"We did not have any specific information about a particular attack in London or any place else before these bombings last week," he said.
Mr. Chertoff said he believes the attacks were carried out by al-Qaida sympathizers, but that it is not clear whether the terrorist group's leader, Osama bin Laden, actually planned them.
When asked if he thought suicide bombers were involved, Mr. Chertoff did not rule it out, but ultimately deferred to British authorities.
"We are going to want to see what the British develop," he said. "That is going to tell us about who may have been responsible, what kinds of tactics we have to worry about. And we are monitoring that on an hourly basis."
Immediately after the London bombings, the Department of Homeland Security raised the threat level to "high" for U.S. transit systems. Secretary Chertoff said his agency will continue to review the threat potential to decide if that designation needs to be changed.