Americans should prepare for more confusion, uncertainty and cynicism as the government continues to learn how to balance its need to raise alarms about a possible terrorist attack without revealing classified information or compromising sources, according to homeland security experts.

Nearly three years after the attacks on New York and Washington, Department of Homeland Security officials long ago lost the ability to simply ask for the public's trust when they suddenly announce new security measures based on intelligence they cannot release, said retired Col. Randall Larsen, a top homeland security consultant to government and the private sector.

Larsen cited Prussian military theorist Karl von Clausewitz, who posited 170 years ago that all armies suffer from two disabilities: "fog and friction" -- lack of information and miscommunication among units.

"Now that all Americans are part of the troops on the battlefield of the U.S. mainland in this war, we're all going to have to live with some of the same ambiguity that war fighters deal with," Larsen said. "Often, things aren't going to be clear to us."

Frank Cilluffo, a former Bush White House counterterrorism official who now heads homeland security programs at George Washington University, said that terrorism alerts such as last Sunday's are designed in part to encourage the public to stay alert for the specific threats at hand.

"The last thing we want is for those responsible for conveying threat information to start second-guessing themselves, which could create a chilling effect" and persuade U.S. officials to stop issuing public warnings, he said. "Stopping the flow of information to the public, which can play such a key role in fighting this war, would not be good for the country."

The confusion began Sunday when senior U.S. intelligence officials described a "treasure trove" of intelligence showing that al Qaeda operatives had cased five major financial institutions in Washington, New York and New Jersey. The next day, the public learned that almost all the al Qaeda surveillance files, taken from a computer seized in Pakistan days before, were compiled in 2000 and 2001. Some critics said this showed officials had overstated the threat.

On Tuesday, intelligence officials, speaking confidentially, responded that they had relied on "multiple streams of intelligence" that they could not reveal -- including interrogations of al Qaeda members in custody and captured documents -- that buttress their belief that terrorists were plotting attacks on financial sites.

On Wednesday, two local police chiefs said they did not know of any new intelligence specific to Washington, beyond what was released publicly. But at the same time, intelligence officials pointed to the dismantling of an apparent al Qaeda cell in Britain that was actively planning attacks on the United States.

Some government officials acknowledged that they could have avoided much of the skepticism if they had said Sunday, when Homeland Security Secretary Tom Ridge first raised the terrorism threat level for three cities' financial sectors to orange, or "high risk" of attack, that almost all the documents the CIA recovered were at least three years old.

But a senior U.S. intelligence official, speaking only on the condition that he or she not be named because the underlying information is classified, acknowledged exasperation at the skepticism expressed by some members of the public when they learned the age of the surveillance files.

"We were doing what we thought was our job, to uphold our sworn duty to protect people [by releasing the information], and now we're being criticized for doing it," the official said. "The detail and specificity of the [computer] reports was so striking and dramatic that we felt we had no choice" but to warn officials and the public in Washington, New York and Newark.

On Wednesday, U.S. Capitol Police Chief Terrance W. Gainer and D.C. Police Chief Charles H. Ramsey said they were not aware of the other streams of intelligence that convinced federal officials that an attack on Washington could be in the offing.

Gainer said that "beyond what Secretary Ridge has said, there is no specific intelligence about an imminent strike in Washington. . . . There is not some smoking gun." Gainer said he had wanted to close streets on Capitol Hill for a long time and that the information he received from the Homeland Security Department was enough to justify that move, which has caused considerable criticism from city officials and the public.

Ramsey said, "There was nothing in the information to cause the kind of reaction we have with street closings and checkpoints. There is not an imminent threat." Ramsey added that he was not uncomfortable with the amount of information he had, merely upset at the decision to close streets and erect checkpoints near the Capitol.

Staff writer Sari Horwitz contributed to this report.

Frank Cilluffo heads homeland security programs at GWU.