Tenet ended the program because the agency could not work out its practical details, the officials told The Associated Press.
Porter Goss, who replaced Tenet in 2005, restarted the program, the former officials said. By the time Michael Hayden succeeded Goss as CIA chief in 2006 the effort was again flagging because of practical challenges.
CIA Director Leon Panetta drove the final stake into the effort in June after learning about the program. He called an emergency meeting with the House and Senate Intelligence committees the next day, informing politicians about the program and saying that as vice president Dick Cheney had directed the CIA not to inform Congress about the operation.
The CIA declined to comment on the officials' comments.
One former senior intelligence official said on Wednesday that the idea never quite died because it was a capability – the details of which remain classified – that the CIA wanted in its arsenal. But as time wore on, the official said, its need became less urgent.
Another former official said that the CIA's reliance on foreign intelligence services and on drone-launched missile strikes proved over time to be less risky yet effective in targeting al-Qaeda chiefs for death or capture. President George W Bush authorised the killing of al-Qaeda leaders in 2001.
According to one congressional official, the agency spent more than $1 million over the eight years that the CIA considered launching the hit teams. The official would not detail the exact amount or how it was spent.
The House Intelligence Committee is laying the groundwork for a possible investigation of the program and its concealment from Congress. In late June it asked the CIA to provide documents about the now-cancelled program to kill al-Qaida leaders.
Agency officials say it is complying with the request. Panetta has at the same time ordered a thorough internal review of the program.
The committee will try to establish how much was spent on the effort, whether any training was conducted and whether any officials travelled in association with the program, a committee official said. Those factors would determine whether the program had progressed enough to require congressional notification.
House Intelligence Committee Chairman Silvestre Reyes is expected to decide as early as this week whether to press ahead with a full investigation.