After his presentation, Mr Powell held private meetings with other members of the Security Council.
US officials claimed that at least two waverers, Chile and Angola, were coming round to Washington's viewpoint.
But reactions from many allies and friends of the US show that the ground is shifting.
In Europe, antagonism to US policy shows signs of fading.
The European Union's foreign policy chief, Javier Solana, says Mr Powell's report was "very solid". For Saddam Hussein, Mr Solana now says, "time is very short".
Ten central and eastern European states, from Estonia to Albania, put out a clear-cut statement of support for the US.
If Iraq continues to defy the will of the UN, they say they will be ready to join in an international coalition to enforce its disarmament.
France, which has hinted it might veto a resolution authorising war, has changed its tone.
French Foreign Minister Dominique de Villepin has started talking about "the Iraqi risk".
He says the use of force is a last resort, but France does not exclude any possibility.
US 'winning over' allies over Iraq