Source: http://www.msnbc.msn.com/id/9671487/
On Hardball Oct 11, 2005, Mrs. Greenspan, AKA Andrea Mitchell, NBC News Foreign Affairs Chief, identified Colin Powell as the "senior Administration source" who pinpointed the July 7, 2003 exposure of Ari Fleischer to the memo which identified Valerie Plame as the wife of Joe Wilson (Fleischer had already announced his resignation as White House Press Secretary in May, but was still in the job at this point). This exposure happened on Air Force One en route to Africa. Subsequently, Plame's identity as a CIA operative was shopped around to reporters in the Washington area and published by Robert Novak (an old acquaintance of Rove's) on July 14. Mind you, initially it was believed that Powell requested the memo to be drawn up, but former NSC staffer, Roger Morris, writing in CounterPunch, states that the memo originated with the State Department's Bureau of Intelligence and Research:
February 19, 2002: A meeting at the CIA discusses sending Wilson to Niger. Attending is an analyst from the State Department Bureau of Intelligence and Research who says the trip is unnecessary, since the US embassy in Niger and European intelligence agencies have already disproved the story of an Iraqi purchase-and whose notes of the meeting, including the facts of Valerie Plame's CIA identity as an NOC operative on WMD and her role in recommending her husband, will be the basis for later crucial memos in the scandal. ...
June 10, 2003: Undersecretary of State Marc Grossman asks the Bureau of Intelligence and Research (INR) for a briefing on the Niger uranium issue, and specifically the State Department's opposition to the continuing White House view that Iraq had tried to buy yellow cake. The resulting memo is dated the same day, and drawn from notes on the February 19 meeting at the CIA on the Wilson mission and other sources. Befitting the sensitivity of the information, the memo is classified "Top Secret," and contains in one paragraph, separately marked '(S/NF)" for "Secret/No dissemination to foreign governments or intelligence agencies, " two sentences describing in passing Valerie "Wilson's" identity as a CIA operative and her role in the inception of the Wilson trip to Niger. This June 10 memo reportedly does not use her maiden name Plame. ...
On June 12, Deputy Sec'y of State Richard Armitage (one of the original PNAC letter signatories) and ... wait for it... John BOLTON (another of the PNAC letter signatories) [now, are you wondering about that appointment as Ambassador to the UN? Was it just to get him out of Condi's hair, or was this a kind of bribe, like Tenet's rather surreal payoff: "George... I cannot abide disloyalty; I want your resignation..." Now, here's a medal. Don't talk about this.??!] get ahold of the memo identifying Wilson's wife as a CIA operative. Armitage requests that a copy of the memo be sent to Colin Powell on July 6th. The name of Valerie Plame appears in this new copy of the June 10th memo. Apparently, it was in Powell's - and then Fleischer's - hands aboard AF1 on July 7th as the entourage headed to Africa. But Powell didn't approve of the political use to which this information was put:
According to WaPo, the "senior official" said of the leak: "Clearly, it was meant purely and simply for revenge."
I'd be really glad to see Colin Powell talking freely about this. The administration treated him like a mushroom during his tenure, and ignored his best-considered advice, just as they have done with so many others, including former Treasury Secretary Paul O'Neill (for the source documents used in his book with Ron Suskind, see The Bush Files).