May 12, 2009 -- As President Bush's top lawyer, Alberto Gonzales pressed counterterror officials to use brutal interrogation techniques on terror suspect Abu Zubaydah in 2002, even when those techniques hindered Zubaydah's cooperation, a former FBI agent who was present is expected to testify Wednesday before Congress.

In the first public testimony of anyone directly involved, former bureau agent Ali Soufan is expected to directly contradict assertions by CIA officials and former Vice President Cheney that the "enhanced interrogation techniques" were successful in prying information out of al Qaeda detainees.

Cheney has said that the CIA interrogation program that began in Thailand in 2002 "saved thousands, perhaps hundreds of thousands of lives."

Soufan, a star FBI agent fluent in Arabic and English, met Abu Zubaydah in Thailand, just days after the al Qaeda suspect was captured after a gun battle in Pakistan. Zubaydah was then the most important operative captured after the 9/11 attacks. The U.S. government selected Soufan and another FBI agent, Steve Gaudin, because they were considered experts at getting al Qaeda suspects to crack.

Soufan will testify that within an hour of Abu Zubaydah's arrival at the secret prison, he was revealing parts of the 9/11 plot and had identified the mastermind, Khalid Sheikh Mohammed. Soufan has contended publicly that the FBI approach to interrogation had been so successful, George Tenet ordered that the gravely ill Zubaydah be kept alive.

According to a former intelligence operative at the scene, Zubaydah's confessions and intelligence collected by Soufan and Gaudin resulted in the CIA determining that "death was not an option" for the prisoner. Tenet wanted Zubaydah kept alive, and to continue talking. A top Johns Hopkins surgeon was flown in to treat Zubaydah, and the two FBI agents helped nurse the terrorist into good health. The former operative tells ABC News that the intelligence continued to flow, as Soufan interviewed Zubaydah in the hospital while tending to his recovery. But that all ended when the CIA's team of specialists and a contractor arrived to take over interrogations.

The CIA Takes Over

When Mitchell arrived in Thailand, a source tells ABC News, the CIA ordered Soufan to follow the psychologist's plan for interrogation. It was, Soufan will tell the Senate, a big mistake.

Soufan intends to testify that most of the useful intelligence from Abu Zubaydah came well before the CIA interrogation team even arrived in Thailand.

Soufan is said to be angry and mystified, eight years later, that Washington overruled him and his team during interrogations of Zubaydah, and handed the reins over to Mitchell.

The CIA has defended its interrogation program as lawful and productive, citing the arrest of so-called Dirty Bomber Jose Padilla, and identifying Mohammed as the result of brutal regimen. Mitchell has refused to comment about his involvement in the CIA interrogation program, telling ABC News that "I have a non-disclosure agreement that will not allow me to comment."

Click here to see Mitchell refusing to talk to ABC News.

White House Role

"It was imposed upon us," says the source. "And not only [at CIA] headquarters, they were getting requests specifically from the White House."

According to an intelligence officer involved in Abu Zubaydah's interrogation, Mitchell had "no idea about intelligence, no idea about interrogations, no idea about interviews."

"Who the hell authorizes these things?" Soufan reportedly asked the chief CIA officer in Thailand, as Mitchell began stripping the prisoner and blasting him with music from the Red Hot Chili Pepppers.

Tactics Bred Resistance

Mitchell used a program that he told those present was called "force continuum," an ascending interrogation program that began with forced nudity, followed by loud music and white noise, temperature manipulation and sleep deprivation for up to 48 hours. According to one officer on the scene, Mitchell said the program was a "strategic approach to diminish his ability to resist" the interrogators.

Soufan, will testify that Zubaydah didn't begin resisting until Mitchell began his tactics, according the source familiar with his upcoming testimony. So, Soufan blew the whistle. According to a Department of Justice inspector general report, Soufan told his superiors at FBI headquarters that Mitchell's interrogation was "borderline torture" and told FBI superiors that he wanted to arrest Mitchell for the treatment of Zubaydah.

Each step of the Mitchell regimen failed, according to the source present at the time. Afterwards, The CIA would ask Soufan and his FBI partner to start interrogating Zubaydah again. "They asked, 'Why does the information stop?'" said the source. "We go in again and we have him re-engage again, and we start producing information." Mitchell then wanted to resume control of the interrogation, telling Soufan, "Now we can do it in a way that we really can break him."

Soufan told Mitchell and others that he was "100 percent sure it was going to fail."

"Couldn't Even Dream"

Former Vice President Cheney has requested that two intelligence reports that he said came from the CIA interrogation program be declassified, saying that the reports will prove that water boarding worked.

Soufan, according to a source, doesn't buy it. Soufan intends to tell the Senate on Wednesday that he "couldn't even dream that the United States would do something like that."

Matthew Cole is a freelance national security reporter. His book, about the CIA rendition program, will be published later this year by Simon & Schuster.

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