WASHINGTON – James B. Comey Jr., nominated to become the nation’s seventh director of the FBI, conceded Tuesday he signed a controversial memo allowing waterboarding but said he first lobbied hard to have the policy toned down.

Comey, who is facing confirmation hearings before the Senate Judiciary Committee, has been hailed by some as a hero for blocking, at least temporarily, a Bush White House surveillance program during his time as deputy attorney general under President George W. Bush. Lately, though, he has come under fire from civil liberties advocates for approving the Office of Legal Counsel memo allowing not just waterboarding but also sleep deprivation and other enhanced interrogation techniques for captured terrorists.

Comey told the senators he personally believes many of the tactics are torture. But he said that in the case of the waterboarding memo in May 2005 he was more concerned with what he called “the critical third question” beyond saying yes or no to its legality: “Should we be doing this and is it appropriate as Americans?” he said he asked himself.

Comey said he urged his boss, then-Attorney General John Ashcroft, to persuade the Bush administration not to implement it. “He took my notes with him to a meeting at the White House and made the argument in full,” Comey said. But “the principals (on the National Security Council) were fully on board with the policy, and so my argument was rejected.”

The memo that Comey finally signed, he said, came from a compilation of several versions and the final form, he said, was toned down. He said he signed the memo knowing he would soon be leaving the Justice Department anyway.

Would he have abruptly resigned had he not already announced his departure? “I would have given it very serious consideration,” Comey said.

Comey’s nomination by President Obama is expected to sail through the committee and the full Senate in time for him to replace Robert S. Mueller III, who by law must step down by Sept. 4. Long past the days when FBI Director J. Edgar Hoover held the post for most of his life, the position now has a 10-year tenure.

While most committee members seemed comfortable with Comey, they still had concerns about the memo.

Committee Chairman Patrick Leahy, D-Vt., said it “led to the treatment of detainees that was contrary to our laws and our values, and this frankly made us less safe. We must never repeat those mistakes. They have left a permanent stain on this great nation.”