Mr Powell's bleak assessment, less than three weeks before Iraqis are due to elect a parliament, reflects what advisers close to the administration and former officials describe as an understanding in the State Department and Pentagon of the depth of the crisis.
But, they say, this is not a view accepted by President George W. Bush.
One counterinsurgency expert said Donald Rumsfeld, defence secretary, had a "brutally accurate" picture of the situation and the potential dangers.
But a member of an influential neoconservative policy group said that such warnings "stop well short of the president".
He said Mr Rumsfeld, criticised for the conduct of the war, had an interest in hiding the true picture from the president.
According to Chas Freeman, former US ambassador to Saudi Arabia and head of the independent Middle East Policy Council, Mr Bush recently asked Mr Powell for his view on the progress of the war. "We're losing," Mr Powell was quoted as saying. Mr Freeman said Mr Bush then asked the secretary of state to leave.
Analysts are concerned that with the departure of Mr Powell and his replacement by Condoleezza Rice, the president's loyal national security adviser, the White House will be further shielded from dissent.
Bush, you started this fuckin' war on a lie and it's not going the way you wanted it to, and now you don't want to hear about it? You're a fucking asshole.