With the destruction of the World Trade Center, and the damage to the Pentagon, the possibility of other coordinated terrorist attacks against the U.S. is a very sobering reality. The new Department of Homeland Security is moving to counter that threat. More from VOA-TV?S Jim Harriott.

It?s an exercise called ?top-off 2?, the first large-scale counter-terrorism drill in the U.S. since the 9/11 terror attacks in 2001. The five-day drill began Monday in the western U.S. city of Seattle, Washington, where a fictitious terrorist group set off a so-called ?dirty bomb?, a blast which injured 100 people and spread a cloud of radiation through the city. Greg Nickels is the Mayor of Seattle.

?For 36 hours, we?re going to be going through an exercise to respond to that kind of radiological attack on our city. ?

At the same time, pneumonic plague has been spreading through the mid-west U.S. city of Chicago with mock victims to begin reporting ?flu-like symptoms? Tuesday. But the double-barreled mock attack has some critics wondering just how useful a planned exercise will really be. Among them, Lawrence Gostin at Georgetown University law center.

?Th element of surprise and panic simply isn?t there as it would be in a real event.?

The Secretary of Homeland Security, Tom Ridge

?We are confident that we will learn much and build on our capacity as is our responsibility every single day.?

The government of Canada, along with the province of British Columbia and the city of Vancouver are also taking part in the 16-million dollar exercise to test just how ready first-responders would be for biological and nuclear attacks.