Dozens of high-level officials joined in a White House drill Saturday to see how the government would respond if several cities were attacked simultaneously by the type of the roadside bombs used against American troops in Iraq.

President George W. Bush went on a bike ride not far from the White House Saturday morning, and did not take part in the test.

White House homeland security adviser Fran Townsend presided over the three-hour exercise that brought the government's highest level homeland security officials to the Eisenhower Executive Office Building next to the White House. All Cabinet agencies were represented by their secretaries or other high-ranking officials, with a total of about 90 participants, said Scott Stanzel, a White House spokesman.

Stanzel said the drill revealed gaps in the government's ability to respond, but also showed that there have been many improvements since Hurricane Katrina exposed federal inadequacies when it devastated the Gulf Coast in 2005. For instance, coordination with state and local authorities and the ability to get federal resources in place quickly — key missteps after Katrina — appeared much better now, Stanzel said.

Townsend and the Homeland Security Council that she heads mapped out in advance a massive disaster involving improvised explosive devices, or IEDs, in 10 U.S. cities at the same time, using a combination of large and small towns, said a senior administration official, speaking on condition of anonymity.

IED attacks are being used by insurgents in Iraq with regularity to kill hundreds of civilians and soldiers in Iraq. Recently, the Bush administration has said that IEDs and other weaponry in Iraq are coming from Iran.

But Stanzel said the test was not inspired by new intelligence or any increased chatter about terrorists' desire to use IEDs inside the United States. He noted that both the World Trade Center bombing in 1993 and the Oklahoma City bombing in 1995 involved homemade bombs.

"The threat of an IED goes back 14 years," he said. "It's important for the administration to prepare for any eventuality, just as we have prepared for a pandemic flu, a smallpox outbreak or a major hurricane."

Indeed, this was the administration's fourth such "tabletop" exercise since the first in December 2005 on a bird flu or other pandemic outbreak.

Townsend's scenario envisioned requests pouring in from state and local authorities, and also assumed many local abilities would be diminished by the scale of the disaster. The discussion began with the period immediately after the attacks, then moved to circumstances gamed out for weeks later. At each point, the agency representatives were directed to detail what they would do, the official said.

The next step is for the Homeland Security Council to study the role play and report on what gaps were revealed, Stanzel said.