The Republican chairman of the House Judiciary Committee pointedly criticized Attorney General Alberto Gonzales Thursday for "stonewalling" by refusing to answer questions about the Bush administration's warrantless eavesdropping program.

Rep. James Sensenbrenner, R-Wis., said Gonzales was frustrating his panel's oversight of the Justice Department and the controversial surveillance by declining to provide information about how the program is reviewed inside the administration and by whom.

"How can we discharge our oversight if, every time we ask a pointed question, we're told the program is classified?" Sensenbrenner asked Gonzales near the start of a lengthy hearing on the department's activities. "I think that ... is stonewalling."

Gonzales did not budge, defending the eavesdropping as lawful and telling Sensenbrenner and other lawmakers on the panel that he would not discuss classified matters.

"I do not think we are thumbing our nose at the Congress or the courts," Gonzales said in response to a question from Michigan Rep. John Conyers, the committee's senior Democrat.

President Bush confirmed in December that the National Security Agency has been conducting the surveillance when calls and e-mails in which at least one party is outside the United States are thought to involve Al Qaeda. Gonzales has been at the center of the administration's defense of the program in the face of criticism from Congress and civil liberties groups.