Colin Powell, regarded with yearning by Europeans as the voice of restraint within the Bush inner circle, has let slip the fatal words. Yes, he told reporters on the flight to the development summit in Johannesburg, there were "real differences" within the administration over how to deal with Saddam Hussein.
But this staking out of a position against hardliners may amount to less than it appears. For one thing, it would be astonishing if there were not differences on an issue of such importance. For another, by staying relatively quiet in the clamour of words over Iraq, he may have placed himself better to win the key arguments.
As Secretary of State, General Powell is in constant contact with foreign opinion, which is overwhelming in demanding that action against President Saddam be taken only with the UN's blessing.
Yesterday President Bush said he would take his case to the UN next week: almost certainly there will be a last effort to get weapons inspectors in before a decision to go to war is taken. Behind the scenes, General Powell is forcing the administration to focus on the "day after" in Iraq, the role America and its allies would play in the political and physical rebuilding needed once President Saddam had gone.
Finally, as a former soldier moulded by experience in Vietnam, he understands the risks of war. The issue pitches him and most of the uniformed military commanders against Vice-President Dick Cheney and the civilian leadership of the Pentagon – called by critics the "chicken hawks" for their advocacy of war now, after having failed to fight in Vietnam 30 years ago.
Caution has always been a distinguishing hallmark of General Powell. As chairman of the Joint Chiefs of Staff under the first President Bush, he was deeply wary of using force in 1991 to drive Saddam Hussein from Kuwait.
Success in the Gulf gave rise to the "Powell doctrine," that America should go to war only from a position of overwhelming strength, with clear-cut objectives and with unequivocal public backing. That also explains his fury, during discussion of the Bosnian war in 1993, when Madeleine Albright, then US ambassador to the UN, challenged him: "What's the point of having this superb military you're always talking about, if we can't use it?"
Powell's icy response then was that the military would accept any mission it was handed, "but that the tough political goals always have to be set first". That was his view then. It remains his view today.