WASHINGTON — The White House has unleashed a hard-line defense of the Bush administration’s spying on Americans without a warrant, claiming that only “credible threats” linked to al-Qaeda have been under surveillance and the snooping is necessary to protect “national security.”

Conveniently, a new Osama bin Laden tape diverted attention from a tidal wave of angry questions about the spying. But targets of the eavesdropping called it a dangerous assault on their constitutional rights, aimed at intimidating people into silence in the face of Bush’s grab for unchecked power.

The warrantless spying secretly ordered by Bush in 2001 includes wiretapping by the National Security Agency and a separate Defense Department project, Operation Talon.

Richard Hersh, an activist with the Truth Project in Palm Beach, Fla., which distributes counter-recruitment literature at local high schools, called surveillance directed at him and his group “absolutely ridiculous.”

“We are exercising our constitutional rights,” he told the World. “Our purpose is to educate teenagers, to give them enough information so that they can make an informed choice about whether to enlist in the military, to help them balance the misinformation they are getting from the recruiters.”

NBC News obtained a secret 400-page Pentagon document that listed the Truth Project as a “credible threat” to national security. The Pentagon sent an agent to spy on the group’s first meeting at the Quaker Meeting House in Lake Worth in 2004, one of almost four dozen similar meetings nationwide infiltrated on Bush-Cheney orders.

The report revealed that the Defense Department spy operation kept tabs on 1,500 “suspicious incidents” such as distribution of antiwar leaflets at high schools, peace vigils and town hall meetings.

Eight people are active in the Truth Project, Hersh said, including Quakers, a 79-year-old grandmother and Hersh himself, partially disabled by a nerve disease that often confines him to a wheelchair.

Hersh added with a chuckle, “Yes, I guess we are a ‘credible threat.’ The truth is always a threat to those who are lying. We are always a threat to illegitimate and unjust powers.”

The Truth Project is not “undermining the troops,” as Bush has charged, Hersh said. “The money wasted in spying on us could be better spent on protecting the troops. Four out of every five Marines who have died could have been saved if they had

better body armor.”

Hersh testified in a Jan. 20 hearing on the illegal spying convened by Rep. John Conyers (D-Mich.), ranking member of the House Judiciary Committee.

Conyers opened the hearing, warning, “We are in a constitutional crisis that threatens the system of checks and balances that has preserved our fundamental freedoms for more than 200 years.”

“There is no better illustration of that crisis than the fact that the president is openly violating our laws by authorizing the NSA to engage in warrantless surveillance of U.S. citizens,” Conyers said. “If we let this president convince us that we are at war, so he can do what he wants, we will let stand the principle that the president alone can decide what laws apply to him.”

Hersh told the hearing that agents “rummaged through the trash, snooped into e-mails, packed web sites and listened in on phone conversations. We know that address books and activist meeting lists have disappeared.”

The American Civil Liberties Union, meanwhile, filed a lawsuit on behalf of a long list of plaintiffs seeking a court injunction stopping the NSA spy operation.

In a statement released by the ACLU, plaintiff Nancy Hollander, an Albuquerque, N.M., civil rights attorney, said she was the target of FBI, CIA and Chicago Police Department spying on her antiwar and civil rights activities in the 1960s, 1970s and 1980s. That was an attempt “to chill my First Amendment rights,” she said. But today “the government has succeeded in chilling my First Amendment rights and jeopardizing my clients’ First, Fourth, Fifth and Sixth Amendment rights. This time the government has gone far beyond listening to what I say in public. … This time the government has invaded not only my privacy but the sacred bond I have with my clients to keep their confidences.”

There is every indication, Hollander said, “that the government has listened to conversations I have with my clients both here and abroad.” She no longer uses phone, fax or e-mail and is forced to travel to speak with clients, lawyers and witnesses around the world.

She concluded, “If the Executive chooses to take it upon itself to ignore the Constitution and the laws Congress has passed, we have no recourse and our democracy is in peril.”