LONDON -- Fresh from talks with President Bush, British Prime Minister Tony Blair said Sunday he believed those opposed to war against Iraq would change their minds when they saw evidence of Baghdad's threat.

Blair, who has been Bush's strongest backer in Europe for action against Iraqi leader Saddam Hussein, returned to Britain from a hastily prepared meeting Saturday with Bush at Camp David to discuss Iraq policy.

Blair said last week his government hoped to soon publish a dossier of evidence on the Iraqi president's efforts to develop weapons of mass destruction.

"This is a challenge not simply for America or for Britain but for the whole of the international community," Blair told reporters.

Other European nations have expressed strong opposition to unilateral U.S. action against Iraq, and some voices in Britain have joined the criticism.

Britain's main union federation, the Trades Union Congress, holds its annual conference beginning Monday and will consider a motion expressing "unequivocal opposition" to military action.

John Edmonds, leader of the GMB general workers' union, said many union members were growing increasingly worried about the threat of war.

"There is an unmistakable feel that the U.S. and U.K. governments are moving toward war," he told Sky News television. "And the overwhelming feeling of the delegates here is that this is not something we should contemplate without total U.N. support.

Rod Eddington, chief executive of British Airways, said Sunday that a war in Iraq could hurt airlines already struggling in the wake of the Sept. 11 terrorist attacks.