Michael Isikoff's brief item in Newsweek about how a high-ranking Qaeda detainee, a key source for the administration's alleged ties between Saddam Hussein and Osama bin Laden, has changed his story:

The apparent recantation of Ibn al-Shaykh al-Libi, a onetime member of bin Laden's inner circle, has never been publicly acknowledged. But U.S. intelligence officials tell NEWSWEEK that al-Libi was a crucial source for one of the more dramatic assertions made by President George W. Bush and his top aides: that Iraq had provided training in "poisons and deadly gases" for Al Qaeda. Al-Libi, who once ran one of bin Laden's biggest training camps, was captured in Pakistan in November 2001 and soon began talking to CIA interrogators. Although he never mentioned his name, Secretary of State Colin Powell prominently referred to al-Libi's claims in his February 2003 speech to the United Nations; he recounted how a "senior terrorist operative" said Qaeda leaders were frustrated by their inability to make chemical or biological agents in Afghanistan and turned for help to Iraq. ...

But more recently, sources said, U.S. interrogators went back to al-Libi with new evidence from other detainees that cast doubt on his claims. Al-Libi "subsequently recounted a different story," said one U.S. official. "It's not clear which version is correct. We are still sorting this out." Some officials now suspect that al-Libi, facing aggressive interrogation techniques, had previously said what U.S. officials wanted to hear. In any case, the cloud over his story explains why administration officials have made no mention of the "poisons and gases" claim for some time and did not more forcefully challenge the recent findings of the 9-11 Commission that Al Qaeda and Iraq had not forged a "collaborative relationship."

...A reason for that silence is perhaps given by an anonymous Bush official quoted by Isikoff:

But officials acknowledge ultimate proof may prove elusive. "It all depends on what your definition of a relationship is," said one.