Finding a "smoking gun" linking Iraq and al Qaeda became the main purpose of the abusive interrogation program the Bush administration authorized in 2002, a former State Department official told CNN on Thursday.

The allegation was included in an online broadside aimed at former Vice President Dick Cheney by Lawrence Wilkerson, chief of staff for then-Secretary of State Colin Powell. In it, Wilkerson wrote that the interrogation program began in April and May of 2002, and then-Vice President Cheney's office kept close tabs on the questioning.

"Its principal priority for intelligence was not aimed at preempting another terrorist attack on the U.S. but discovering a smoking gun linking Iraq and al Qaeda," Wilkerson wrote in The Washington Note, an online political journal.