More than ever, the terrorism threat comes from radical Islamic elements, according to RMS. Meanwhile, other groups, such as those representing Tamil and Nepal dissidents, were said to have lessened their activities.

But while the establishment of a constitutional government in Iraq could provide some stability in that country, it could result in terrorists there returning to their native lands to promote further destruction on their home ground, Mr. Coburn noted.

One new threat RMS has factored into its model is the possibility of sabotage of trains or trucks carrying hazardous materials such as chlorine.

Also, jihad groups have expressed new interest in developing poisons that are relatively easy to procure and manufacture, such as the toxin ricin. “It is mainly for the psychological impact, because it would be difficult to kill a lot of people through these methods,” Mr. Coburn said.

The response to Hurricane Katrina has also factored into the new model since it shows “that while plans may look good on paper, there is always a good possibility for screw-ups and failure,” he said.

New York City received plaudits for its concentration on intelligence gathering activities rather than mere fortification. Mr. Coburn said the city has 250 such intelligence agents both at home and abroad. But the city still ranks just after Washington as the top terror target, and faces more potential damage because of the nature of the two cities.