WASHINGTON: The powerful deputy director of the CIA, alleged to have played a role in allowing brutal interrogations of terror suspect, plans to step down in May, the spy agency's chief said Wednesday.

Steve Kappes, who helped manage counter-terrorism operations under former president George W. Bush and worked for years in clandestine operations, will be succeeded by career intelligence analyst Michael Morrell, the CIA's director, Leon Panetta, said in a statement.

Panetta praised Kappes for his "advice and experience," saying he had expressed a wish to retire from the agency for some time.

"So when he told me a few months ago that it was time for him to move on, I understood. Steve has, to put it simply, more than met the highest standards of duty to the nation," Panetta said.

The director portrayed the change at the CIA's number-two post as a smooth transition for an agency rattled by internal shake-ups in the years following the September 11 attacks.

Kappes has been praised for his acumen in and outside the agency, including a delicate mission in 2003 to persuade Libyan leader Moamer Kadhafi to give up his country's chemical and biological weapons program.

But he has also faced questions about his part in controversial tactics against terror suspects under the previous administration.

Some lawmakers had favored him for the top spot at the CIA and lobbied the White House for Kappes to stay on as deputy when Panetta was nominated for the director's post by President Barack Obama last year.

Kappes was seen by senators as a seasoned hand while Panetta came to the job with no experience in the intelligence world.

After the attacks of September 11, 2001, Kappes served as a senior official in the CIA's Directorate of Operations, which supervised a secret program that encouraged harsh interrogations - a program that rights groups say amounted to torture.

Kappes has previously denied playing a direct role in the interrogation program.

Fluent in Farsi and Russian, Kappes reportedly worked as a CIA station chief in Frankfurt, Moscow and New Delhi, managing numerous secret operations.

When Obama visited CIA headquarters last year in Langley, Virginia, he praised Kappes as the "graybeard" at the agency.

Kappes, a former US Marine officer, joined the agency in 1981 and rose through the ranks before resigning in 2004 after reportedly falling out with aides to then CIA director Porter Goss.

He returned to the spy service in 2006, when he was named deputy director. Kappes's successor, Morrell, was reportedly accompanying ex-president Bush in Florida when word came of the September 11 attacks.