A Democratic senator says he will block President Bush's nominee to become the CIA's top lawyer indefinitely over concerns that the agency's interrogation techniques may not be legal.

"I'm going to keep the hold until the detention and interrogation program is on firm footing, both in terms of effectiveness and legality," Sen. Ron Wyden, D-Ore., said Wednesday.

Wyden said he was troubled that John Rizzo — who is serving as the CIA's interim general counsel — did not object to a 2002 memo authorizing interrogation techniques that stop just short of inflicting pain equal that accompanying organ failure or even death.

Wyden also said he was concerned that an executive order Bush issued last month did not clarify legal guidelines regarding CIA detentions and interrogations.

"I am not at all convinced that the techniques outlined in these guidelines are effective, nor am I convinced that they stay within the law," said Wyden, a member of the Senate Intelligence Committee.

"The last thing that I want to see is hardworking, well-intentioned CIA officers breaking the law because they have been given shaky legal guidance," he said.

Spokesman Mark Mansfield said CIA Director Michael Hayden strongly supports Rizzo's nomination, noting that Rizzo would be the first general counsel to come up through the ranks of the CIA. Rizzo has been with the agency for more than three decades and served as acting general counsel from 2001 to 2002 and again since August 2004.

"Mr. Rizzo's objective has been and continues to be to give the CIA the legal framework it needs to help protect our country in full and strict accord with the laws and treaty obligation of the United States," Mansfield said.

The agency's terrorist interrogation and detention program has been implemented lawfully and with great care, Mansfield said: "It has produced vital information that has helped our country disrupt terrorist plots and save innocent lives. The United States does not conduct or condone torture."

At a public hearing in June, Rizzo said he did not object to the 2002 memo that said for an interrogation technique to considered torture, it must inflict pain "equivalent in intensity to the pain accompanying serious physical injury, such as organ failure, impairment of bodily function, or even death." He said he later found the document to be an "aggressive, expansive" reading of U.S. law.

Under Senate rules, a single senator, sometimes anonymously, can put a hold on legislative action for months. Wyden makes a practice of announcing his holds.