US Defence Secretary Donald Rumsfeld has cast doubt on whether there was ever a relationship between Saddam Hussein and al-Qaeda.
Rumsfeld's comments can be revealing
The alleged link was used as a reason by President Bush for invading Iraq.
Mr Rumsfeld was asked by a New York audience about connections between Saddam Hussein and Osama Bin Laden.
"To my knowledge, I have not seen any strong, hard evidence that links the two," he said, though he later issued a statement saying he was misunderstood.
When asked about the putative link during a session at the Council on Foreign Relations in New York on Monday, the defence secretary said: "I have seen the answer to that question migrate in the intelligence community over a period of a year in the most amazing way."
The BBC's diplomatic correspondent Jonathan Marcus says Mr Rumsfeld's blunt admission seems to give added weight to one of Democratic presidential challenger John Kerry's most telling punches, when he accused President Bush of fighting the wrong war for the wrong reasons.
However, he adds that the minds of many voters may already be made up.
In the past, Mr Rumsfeld has spoken of credible information about a link, while Vice-President Dick Cheney regularly goes further and talks of Saddam Hussein having provided safe harbour and sanctuary for al-Qaeda.
Several hours after his appearance, Mr Rumsfeld issued a statement saying his comments had been "regrettably misunderstood" and that he had acknowledged there were ties between Osama Bin Laden and Iraq based upon CIA intelligence.
This included "solid evidence of the presence in Iraq of al-Qaeda members, including some that have been in Baghdad", he said.
On Monday, Mr Rumsfeld also said intelligence about weapons of mass destruction before the invasion had been faulty and that the US had been unable to find any such weapons.
"Why the intelligence proved wrong, I'm not in a position to say, but the world is a lot better off with Saddam Hussein in jail," he said.
Mr Rumsfeld added that Saddam Hussein's regime was not the "Little Sisters of the Poor" - Iraq had been on the US State Department's terrorist list and made payments for Palestinian suicide bombings, he said.
"The relationships between these folks are complicated. They evolve and change over time. In many cases, these different networks have common funders."
He also said that although most of al-Qaeda's senior leaders had sworn an oath to Osama Bin Laden, the man suspected to be the principal leader of the network in Iraq, Abu Musab al-Zarqawi, had not.
Mr Zarqawi's reported presence in Baghdad before the war has been cited in the past by the US administration as evidence of a link between Saddam Hussein and al-Qaeda.
The former US governor of Iraq, Paul Bremer, said on Monday the US had made two mistakes in the conflict in Iraq - although he was still in favour of intervening in Iraq.
One error was not having enough ground troops to take control of the country, he said.
The US also made the mistake of not containing the violence and looting quickly
enough after Saddam Hussein was ousted, he said.
"We paid a big price for not stopping it because it established
an atmosphere of lawlessness," he told a conference in West Virginia.