By curtailing its undercover investigation of the two groups, the bureau lost a "golden opportunity" to infiltrate a potentially deadly union between two violent radical organizations, according to a former FBI agent involved with the case.
The document reviewed by ABC News contained several redacted excerpts of a 157-page FBI transcript from a secret recording on Jan. 23, 2002 between a known Islamic terrorist supporter and an established member of a white supremacist group in Florida. It shows the two men discussed killing Jews and journalists, praised Hitler and Palestinian suicide bombing efforts in Israel and discussed general ways the two men could work together by using front companies and sharing resources.
"[T]he enemy of my enemy is my friend," the Islamic terrorist supporter said to the white supremacist at the 2002 meeting, according to the transcript, which was recently obtained from the FBI and entered into congressional testimony by Sen. Charles Grassley, R-Iowa.
"That's where we're comin' from," the supremacist responded.
"Anybody that's willing to...to shoot a Jew or to hit a Jew is my friend. Automatically," the transcript shows the Islamic terrorist supporter saying in response.
ABC News was allowed to take notes from the transcript excerpts, which are set for imminent publication in the Congressional Record, but was not allowed to make a verbatim copy of the entire document.
The FBI and the Department of Justice Inspector General have insisted the conversation had no significant connection to terrorism. But one veteran FBI counterterrorism agent told ABC News that's hard to fathom.
"There's no way you can discount this," Jack Cloonan, an ABC News consultant, said. Cloonan, who spent 27 years with the bureau and was the senior agent of its bin Laden unit, cautioned that it was hard to make conclusive statements about the transcript after reading only excerpts, but that he was alarmed by what he saw.
"I'm shocked, frankly, that this is the position the bureau is taking," Cloonan said. A discussion between known Aryan and Islamic extremists in which they praise violence and talk warmly of working together -- "this is what the FBI has said it's worried about," Cloonan said. "As a counterterrorism agent, this is what you live for."
The FBI did not immediately respond to requests for comment.
Months after the Sept. 11, 2001 terrorist attacks, a secret FBI informant helped agents from the Tampa, Fla. FBI office surreptitiously record the meeting between a man the bureau knew to be a known Islamic terrorist supporter and another man, an established member of a white supremacist group, in Florida.
Neither the men's identities nor the identities of the groups they represented were included in the transcript. At one point, the supremacist referred to the Palestinian group Hamas, which has staged suicide attacks against Jews in Israel.
"Just like Hamas. Not everybody in the occupied territories has that determination, that will, to do what has to be done," the supremacist states, according to the transcript.
After an FBI agent who was called in to consult on the operation raised concerns about how the recording was made and how the case was being documented, the office cut short the undercover investigation.
At first, agents from the case denied any recording had been made, according to a January 2006 Justice Department Inspector General's report.
The Inspector General concluded that FBI agents mishandled the case, falsified records and made misleading statements in connection to the recording. The report also confirmed that senior FBI officials had retaliated against the agent who had called attention the problem, Michael German.
German, a veteran undercover FBI agent who specialized in infiltrating white supremacist groups, left the bureau in 2004, after being barred from helping train new FBI recruits in undercover tactics. German has said that the FBI lost a "golden opportunity" by failing to conduct further investigation into the possible union.
The transcript "flatly contradicts statements made by bureau officials trying to downplay the incident and discredit Michael German," said Sen. Charles Grassley at a recent hearing. Grassley also challenged the reasoning of Inspector General Glenn A. Fine, whose report agreed with Tampa FBI officials that "no terrorist threat was missed."
This post has been revised.