Military alert level raised to 'high'
Pentagon military police wearing bulletproof gear
WASHINGTON (CNN) -- The Defense Intelligence Agency (DIA) has raised the military terror threat level from "significant" to "high," its top level, as the nation braces for a possible terrorist attack.
The DIA decision, made Tuesday, has been communicated worldwide to military commanders who will review security procedures at their bases. Base commanders will decide whether to alter their "force protection" standards, which detail security standards around military bases.
It's not clear, however, what specific impact the DIA decision will have. Most domestic bases are at Condition Bravo, which calls for restricting access to bases to authorized personnel and conducting ID checks. Commanders could add additional measures.
Some overseas bases, especially in the Persian Gulf, are already at the higher level, Condition Charlie, and it's not apparent whether other measures will be taken.
But at the Pentagon, which has been at Condition Charlie since the September 11, 2001, attacks, military police inside and outside the building Wednesday were in bulletproof vests and helmets.
So far there have been no specific orders to increase combat air patrols over the U.S. or to deploy Stinger missile batteries, as has been done in the past. But one official said those orders could be forthcoming and that the military would continue to change its security procedures in the days ahead.
The DIA "high" level is defined as: "Terrorists are operationally active and these terrorists are known to use large casualty-producing attacks," one official told CNN.
In addition, the "high" level is characterized by concern about areas of large military presence and in which "the environment is known to favor terrorists."
The information is based on recent communications intercepts and interrogation information from top terrorist suspects in custody -- including Khalid Sheikh Mohammed, alleged to be the mastermind behind the September 11 attacks, the official said.
Intelligence sources also believe that al Qaeda operatives have been dispatched to the United States.
On Tuesday, officials raised the nation's civilian alert to "high" -- the second highest level of warning. Previously it was "elevated." (Flash interactive: Raising and lowering threat level)
Officials have offered no details about a time and place for any attack, but both military and civilian officials said they have intercepted communications from suspected terrorists showing something may happen. (On the Scene: CNN's Jeanne Meserve)
FBI Director Robert Mueller said on ABC News' "Good Morning America" show in a live interview from the FBI Academy in Quantico, Virginia, that intelligence shows that recent attacks in Morocco and Saudi Arabia "might be a prelude to an attack in the United States."
"I want to point out that we had no specificity as to targets," Mueller said. "We had no specificity as to exact time. And the American public wants to go about its business, understanding that it is has to be vigilant, more alert during this period of high risk."