Joseph Wilson, the former ambassador to Iraq in the run-up to the first Gulf War, was the last US diplomat to meet with Saddam Hussein, in 1991.
Wilson was also the man the US government sent to Niger in 2002 to investigate claims it had sold yellow cake uranium to Iraq.
He found nothing.
But the UK and US governments still said Saddam had been trying to buy the substance from an African nation.
Wilson refuted the claims after the Iraq war began.
Within a week, the Washington Post newspaper had outed his wife as a CIA agent and the two of them were placed at the centre of a huge US scandal.
In an interview with Al Jazeera's Mike Hanna, Wilson talked about the motives behind the Bush administration's decision to go to war in Iraq and the consequences the US suffered following the 9/11 attacks.
"I believed that the facts that had been conveyed by the president to the American people were not facts at all, were not sustained at all by the intelligence we had," Wilson said.
"I believed that we had a right as citizens to know the exact reasons we went to war and if in fact we had been dis-served, if the intelligence had been misleading, that we had been misled into a war of choice, rather than a true war of national security.
"I think the consequences to the United States have been really rather dire indeed. It has cost us blood, it has cost us treasure," he said.
"But even more than that, it has cost us, I think, our moral standing and our international political leadership capacity in the world."