WASHINGTON, July 30 - A senior leader of Al Qaeda who was captured in Pakistan several months after the Sept. 11 terrorist attacks was the main source for intelligence, since discredited, that Iraq had provided training in chemical and biological weapons to members of the organization, according to American intelligence officials.
Intelligence officials say the detainee, Ibn al-Shaykh al-Libi, a
member of Osama bin Laden's inner circle, recanted the claims sometime
last year, but not before they had become the basis of statements by
Mr. Libi, who was captured in Pakistan in December 2001, is still being held by the Central Intelligence Agency at a secret interrogation center, and American officials say his now-recanted claims raise new questions about the value of the information obtained from such detainees.
A report in Newsweek magazine several weeks ago first identified Mr. Libi's role in the episode. And the fact that "an Al Qaeda operative" who had provided the most detailed information alleging such ties had backed away from many of his claims was mentioned by the Sept. 11 commission in a brief footnote to the report it issued this month.
The American officials now say still-secret parts of the separate report by the Senate Intelligence Committee, which was released in early July, discuss the information provided by Mr. Libi in much greater detail. The Senate report questions whether some versions of intelligence reports prepared by the C.I.A. in late 2002 and early 2003 raised sufficient questions about the reliability of Mr. Libi's claims.
Separate from the question of Mr. Libi's account, an internal C.I.A. review of its prewar intelligence on Iraq is still under way, continuing a push to evaluate the information used as a rationale for war. The strongest White House assertions of ties between Iraq and Al Qaeda that involved illicit weapons were made beginning in October 2002, when Mr. Bush said in a speech in Cincinnati that "we've learned that Iraq has trained Al Qaeda members in bomb making and poisons and gases."
In the prelude to the American invasion in March 2003, those claims were echoed often by Mr. Bush and his top advisers, but they have not repeated that allegation for at least six months.
Intelligence officials declined to say precisely when Mr. Libi changed his account, and they cautioned that they still did not know for sure which account was correct. They said they would not speculate as to whether he might have been seeking to deceive his interrogators or to please them by telling them what he thought they wanted to hear.
But the intelligence officials said Mr. Libi had backed away from many of his earlier claims after American interrogators presented him with conflicting information. Both Khalid Shaikh Mohammed and Abu Zubaydah, two other high-ranking Qaeda operatives now in American custody, have told interrogators that Al Qaeda had no substantive relationship with the Iraqi government, according to the Senate report.
Neither the Senate committee nor the Sept. 11 commission have found evidence of a collaborative relationship between Iraq and Al Qaeda on any matter, much less illicit weapons, which have not been found in Iraq despite more than a year of intensive searching.
Mr. Libi's reversal was reported to senior administration officials in an intelligence document that was circulated on Feb. 14, 2004, the intelligence officials said.
The Senate report says that a highly classified report prepared by the C.I.A. in September 2002 on "Iraqi Ties to Terrorism" described the claims that Iraq had provided "training in poisons and gases" to Qaeda members, but that it cautioned that the information had come from "sources of varying reliability."
By contrast, it noted that unclassified testimony to Congress in February 2003 from George J. Tenet, then the director of central intelligence, had not included any caveats and thus "could have led the recipients of that testimony to interpret that the C.I.A. believed the training had definitely occurred."
Most public statements by Mr. Bush and other administration officials on the matter described the assertions as matters of fact.
At the time of his capture, Mr. Libi, a Libyan, was the highest-ranking Qaeda leader in American custody. He had worked closely with Abu Zubaydah at the group's Khalden terrorist camp in Afghanistan, and was believed to have detailed knowledge of the terrorist network's plans.
In an address to the United Nations Security Council in February 2003, Mr. Powell referred at length to Mr. Libi's account of an Iraqi role in illicit weapons training, though he did not identify him. He attributed the account to a "senior Al Qaeda terrorist" who "was responsible for one of Al Qaeda's training camps in Afghanistan."
The support by Iraq included "offering chemical or biological weapons training for two Al Qaeda associates beginning in December 2000," Mr. Powell said in his speech, adding that a militant known as Abu Abdullah al-Iraqi had described as "successful" a relationship in which he was sent to Iraq several times between 1997 and 2000 "for help in acquiring poisons and gases."
In recent months, Mr. Powell has spoken publicly of his frustration that some of the central assertions he made in that speech, particularly claims that Iraq possessed illicit weapons, have not been borne out by the facts, despite assurances from Mr. Tenet and the C.I.A. that they were based on solid intelligence.
People close to Mr. Powell say he is less troubled about the episode involving Mr. Libi, believing that the C.I.A. reported his claims in good faith. Similarly, Congressional officials said, the Senate Intelligence Committee did not criticize the C.I.A., even in the classified section of its report, over the Libi matter.
Intelligence officials said Friday that John E. McLaughlin, the acting intelligence chief, was reviewing a 20-page report by Richard J. Kerr, a former deputy director of central intelligence, that constitutes the agency's most extensive internal review of its handling of prewar intelligence on Iraq. The report by Mr. Kerr, which was submitted to Mr. McLaughlin on Thursday, is not expected to be made public, a senior intelligence official said.