Colin Powell, the former US secretary of state, has said he regrets providing misleading intelligence that led the US to invade Iraq, believing it had weapons of mass destruction.
Powell, the first secretary of state in the administration of George W. Bush, the former US president, which declared war on Iraq in 2003, told Al Jazeera on the 10th anniversary of the worst terror attacks on US soil that the information was a "blot on my record".
"It turned out, as we discovered later, that a lot of sources that had been attested to by the intelligence community were wrong," Powell said in Washington, DC.
"I understood the consequences of that failure and, as I said, I deeply regret that the information - some of the information, not all of it - was wrong," said the former chairman of the Joint Chiefs of Staff.
"It has blotted my record, but - you know - there's nothing I can do to change that blot. All I can say is that I gave it the best analysis that I could."
Powell, who was secretary of state from 2002 to 2005, gave an elaborate description of Iraq's weapons programme in the run-up to the war, saying "ambition and hatred" were enough to bring Iraq and al-Qaeda together and build more sophisticated bombs.
"I gave that speech on a four days' notice based on an intelligence estimate that had been done months before and provided to Congress, and every word in that speech was gone over by the director of the Central intelligence Agency (CIA) and his deputy director and all experts," he said.
In the United Kingdom, a traditional ally of the US which backed the military campaign, Tony Blair, who was prime minister at the time of the invasion, said Iraq had the capacity to deploy weapons of mass destruction in 45 minutes.
Blair has since been criticised for allegedly exaggerating that claim and for presenting intelligence that overstated the case for going to war. But Powell said he did not exaggerate the information he presented to Congress.
"There is nothing that I made up; there's nothing that I stuck in there," he said.
"Some people tried to stick extra things in there that the intelligence community wouldn't verify and I said 'no'.
"And so when I presented that information, it was information that the president believed in; information that my colleagues in government believed in."
Powell said he "presented the best evidence that we had" and that the United Kingdom and other nations believed it.
The US invaded Iraq about 18 months after commercial airliners were hijacked by 19 men affiliated to al-Qaeda and flown into the twin towers of the World Trade Centre in New York.
Up to 3,000 people were killed by the hijackers who also targeted the Pentagon.
The war in Iraq, in which the US lost 6,000 of its soldiers, was preceded by the invasion in 2001 of Afghanistan by Washington.
Afghanistan was then home to Osama bin Laden, the mastermind of the 9/11 attacks and leader of al-Qaeda who was killed in May in Pakistan by US forces after a manhunt lasting nearly a decade.