The lawsuits would be thrown out if telecom companies show that they were told by government officials that surveillance orders were legal.

The amendment that delays a court decision on telecom immunity was offered by Senators Jeff Bingaman, a New Mexico Democrat; Robert Casey, a Pennsylvania Democrat; and Arlen Specter, a Pennsylvania Republican. Nine Democrats and one independent, including Reid, have offered the amendment to kill the legal immunity provisions outright.

The Bush administration has briefed only a limited number of lawmakers on the details of the surveillance program, Specter said Tuesday. Congress has had little success policing the Bush administration's surveillance efforts, making lawsuits the only way for U.S. residents to get details about the program, he said.

"Most of the members of Congress do not know what we're giving retroactive immunity on," Specter said on the Senate floor. "Given the ineffectiveness of Congress ... the only recourse we have now is the courts."

The telecom immunity provisions would open the door for future illegal spying programs, added Senator Russ Feingold, a Wisconsin Democrat who cosponsored the amendment to remove the immunity provisions. "Doesn't it send a terrible message, doesn't it set a terrible precedence to give [carriers] a get-out-of-jail-free card?" he said Tuesday.

But supporters of the bill and the immunity provisions argued that legal protections are necessary for carriers that helped the U.S. government fight terrorism after the Sept. 11 attacks on the U.S.

"Liability protection is the fair and just result and is necessary to ensure the continued assistance of the private sector," wrote Mukasey and McConnell.

Lawmakers have a right to be angry that the Bush administration cut out Congress and the courts when rolling out the surveillance program, said Senator Jay Rockefeller, a West Virginia Democrat and chairman of the Senate Intelligence Committee. But the FISA Amendments Act is about "moving forward," he added.

The bill spells out that surveillance programs must be approved by a FISA court, and it requires inspector-general reports on the program, he said. In addition, it makes clear that carrier participation in a surveillance program without court approval is illegal going forward, he said.

The lawsuits against telecom companies won't uncover the truth about the surveillance program, Rockefeller said. The people suing the carriers "never have and will never be" given classified information about the program, he said.