A US former Deputy Secretary of State, Richard Armitage, has admitted that he first disclosed that Valerie Plame was an undercover CIA agent.
Mr Armitage said he was not part of a conspiracy to out Ms Plame
Her outing, in 2003, led to accusations of a smear campaign by the White House against opponents of its Iraq policy.
Mr Armitage said his revelation had been "a terrible mistake", one which he had made inadvertently, thinking Ms Plame's job was not secret.
Ms Plame's husband, a diplomat, openly questioned US policy ahead of the war.
There were widespread accusations that Ms Plame's identity had been disclosed in revenge for an article Joseph Wilson had written criticising the Bush administration's use of intelligence to allege that Iraq had tried to buy uranium from Niger.
Mr Armitage's admission, made in a flurry of US media interviews, follows a series of news reports in late August identifying him as the source of the leak.
"I did what I did," Mr Armitage told the Associated Press. "I embarrassed my president, my secretary, my department, my family and I embarrassed the Wilsons. And for that I am very sorry."
He described one conversation where he had told columnist Robert Novak that he thought Mr Wilson's wife worked in Niger - and a second in which he had told Washington Post reporter Bob Woodward that this was the case.
Ms Plame and her husband say she was "betrayed"
He said the revelation had not been made maliciously and that he was not part of a conspiracy to reveal Ms Plame's identity and did not know whether one existed.
Mr Armitage told the New York Times he had wanted to disclose his role earlier, but had been asked not to by the prosecutor investigating the leak, Patrick Fitzgerald.
Knowingly disclosing the identity of a covert CIA agent is against US law.
No officials have been charged with leaking Ms Plame's identity, although a former adviser to the vice-president Dick Cheney, Lewis "Scooter" Libby, is awaiting trial for allegedly obstructing justice.
After news reports began to name Mr Armitage as the source, a lawyer working for Ms Plame and Mr Wilson said they still planned to go ahead with a lawsuit against close associates of President George W Bush.
The couple filed a suit in July against Vice-President Dick Cheney; his former chief of staff Lewis "Scooter" Libby; and Karl Rove, George W Bush's top political adviser, accusing them of intentionally revealing Ms Plame's identity to discredit Mr Wilson.