Members of President-elect Barack Obama's incoming administration spent several hours at the White House on Tuesday rehearsing how they would respond if terrorists detonate bombs in several American cities at once.
The White House dubbed it "war gaming."
Mr. Obama's incoming chief of staff, Rahm Emanuel, said it was "a very, very important meeting."
"You have to go through this exercise, understand the responsibilities and what happens," he said.
White House deputy press secretary Scott Stanzel said that Mr. Obama's senior staff and Cabinet appointees began the morning with briefings in the White House Situation Room before observing the federal government's response to a simulated attack.
"Using a hypothetical scenario where improvised explosive device attacks have been carried out in numerous American cities - including transportation networks and economic infrastructure - leaders had a discussion about how the federal government would respond and manage the crisis," Mr. Stanzel said.
"This was a realistic and conceivable scenario, but was not based on any current credible threat," he said.
The nearly three-hour exercise was coordinated by a former White House official, Joel Bagnal, who resigned last year from his post as deputy White House homeland security adviser.
White House Chief of Staff Joshua B. Bolten and White House homeland security adviser Ken Wainstein presided over the operation Tuesday.
Along with nine senior White House staff members, the heads of every federal agency involved with domestic security or policymaking attended. Mr. Emanuel brought the men and women who will replace them, along with David Axelrod and Robert Gibbs, who will serve as senior adviser and press secretary to Mr. Obama, respectively.
In addition to the IED scenario, participants also discussed "air defense, pandemic influenza and other disaster-response situations," Mr. Stanzel said.
Despite the fact that the term IED first entered the American lexicon after the bombs were used against U.S. troops in Iraq, homeland security expert David Heyman said the weapons constitute "the weapons of choice for terrorist groups all over the world."
"It's the most likely scenario that an incoming team would face," said Mr. Heyman, who oversees the homeland security program at the Center for Strategic and International Studies.
"What do you do? How do you protect people? What do you say to them? How do you coordinate your protection plans?" he said.
The magnitude of coordinating such a response was not lost on Mr. Emanuel, who applauded Mr. Bush's decision to include the president-elect's team in an exercise that the federal government conducts about four times each year.
"This is just one example of what has been ... an unprecedented integration of transition," said Mr. Emanuel, who regularly criticized Mr. Bush when he was a Democratic leader in Congress.
"And I cannot thank President Bush as well Josh enough for their efforts in making sure that this transition is seamless," Mr. Emanuel said.