"Is it the government's position that when our country is engaged in a war that the power of the executive when it comes to wiretapping is unchecked?" Judge Harry Pregerson asked a government lawyer in a tone of incredulity and frustration.

Gregory G. Garre, a deputy solicitor general representing the administration, responded that the courts have a role, though a limited one, in assessing the government's assertion of the so-called state secrets privilege, which can require the dismissal of suits that could engender national security. Judges, he said, must give executive branch determinations "utmost deference."

"Litigating this action could result in exceptionally grave harm to the national security of the United States," Garre said, referring to the assessment of intelligence officials.

The three judges, on the 9th U.S. Circuit Court of Appeals, were hearing arguments in two combined lawsuits challenging the highly classified surveillance programs, which the administration said were essential in combatting international terrorism. The appeals were the first to reach the court after dozens of suits against the government and telecommunications companies over NSA surveillance were consolidated last year before the chief judge of the federal trial court here, Judge Vaughn R. Walker.

The appeals concern two related questions that must be answered before the merits of the challenge can be considered: whether the plaintiffs can clearly establish that they have been injured by the programs, giving them standing to sue; and whether the so-called state-secrets privilege requires dismissal of the suits on national security grounds.

Though the questions are preliminary, the impact of the appeals court's ruling may be quite broad. Should it rule for the government on either ground, the legality of the NSA programs may never be adjudicated.

All three judges — appointed by Democratic presidents — indicated that they were inclined to allow one or both cases to go forward for at least limited additional proceedings before Walker.

The two cases deal with different secret programs, but are broadly similar. One, a class action against AT&T, focuses mainly on allegations that the company provided the NSA with its customers' phone and Internet communications for a vast data-mining operation. The lawyers in the AT&T case call that program, which the government has not acknowledged, a "content dragnet."

The second case, brought by an Islamic charity and two of its lawyers against the government, concerns a targeted program which the Bush administration calls the Terrorist Surveillance Program. The program, which has since been submitted to a secret court's supervision, bypassed court warrants to monitor international communications involving people in the United States.