Washington - A former No. 2 State Department official in the Bush administration says he would have resigned if he had known the CIA was subjecting terrorism suspects to waterboarding, an interrogation technique that simulates drowning.

    Richard Armitage, the former deputy secretary of state, told Al Jazeera English television in an interview airing Wednesday that waterboarding is torture. However, he said he does not believe CIA officials who engaged in waterboarding and other forms of harsh interrogation should be prosecuted.

    The CIA has acknowledged using waterboarding on three high-level terror detainees in 2002 and 2003, with the permission of the White House and the Justice Department.

    "Had I known about it at the time I was serving, I would've had the courage to resign. But I don't know. It's in hindsight now," Armitage said in the interview.

    Armitage left the Bush administration after President George W. Bush was re-elected in November 2004. He announced he was leaving the day following the resignation of Colin Powell, Bush's secretary of state.

    Armitage told Al Jazeera English television that no one at the State Department knew prisoners were being abused until the Abu Ghraib scandal revealed it to the world in April 2004.

    Congress is at least as much to blame as Bush administration officials for prisoner abuse, he said, because lawmakers failed to conduct rigorous oversight of the detention, interrogation and rendition programs.

    "They weren't doing their job," he said.

    In one of his first acts in office, President Barack Obama ended the CIA's harsh interrogation program, limiting the agency to methods approved by the military. He also approved the closure of the jail at Guantanamo Bay Naval Base in one year.

    CIA Director Leon Panetta told Congress last week that the secret sites where CIA prisoners were waterboarded and interrogated by other harsh means are being closed down, and that he has no intention of prosecuting any CIA employees for their role in the secret program that was deemed legal at the time.

    Attorneys for one of the three prisoners who was waterboarded asked Panetta this week to preserve the black sites to be used as evidence in his trial.