Australian Prime Minister John Howard has suffered a historic defeat in the upper house of Parliament over his handling of the Iraq crisis. Opposition parties passed a motion of no-confidence in the government, illustrating the deepening divide in Australia over the country's involvement in any war in the Gulf.

It is the first time in more than 100 years an Australian prime minister has suffered a vote of no-confidence in the Senate. The motion condemns the government's decision to deploy troops to the Persian Gulf in preparation for war.

Australia and Britain are the only countries so far to join the United States in moving troops to the Middle East as the build-up toward a war with Iraq continues.

Senators from the main Labor opposition combined with the leftwing Greens, Democrats and Independents on Wednesday to pass the no-confidence vote by 34-31.

The Senate also declared its opposition to an attack on Iraq by the United States and its allies, including Australia, and insisted the disarmament of Iraq should only proceed under the authority of the United Nations.

The no-confidence motion is an embarrassment to the conservative administration and is a symbolic victory for the opposition. It does not, however, carry any legislative authority and does not weaken Mr. Howard's position as prime minister.

There is more unease for the Howard government on a leaked diplomatic correspondence between Australia and New Zealand, which suggests the prime minister has already committed his forces to a war in Iraq.

Mr. Howard has denied the allegations, claiming the memo refers to Australian navy vessels patrolling an exclusion zone in the Gulf.

The Labor leader Simon Crean is not convinced. He thinks an e-mail from the mother of a serviceman aboard the HMAS Kanibla, a navy ship heading to the Persian Gulf, proves Australia has been ready for war for months.

"The mother of one of the troops on the Kanibla has just blown him out of the water in that regard," he said. "She says that the preparations for the deployment in relation to the Gulf and support for a war in the Gulf was taking place back in September and October."

On Tuesday, Prime Minister Howard told Parliament that military action was the only language Iraqi President Saddam Hussein could understand and it is time the international community deals with the threats his regime poses to the rest of the world.

The United States says Iraq has been developing weapons of mass destruction in violation of United Nations resolutions and the terms of its 1991 surrender in the Gulf War. Washington says that Baghdad must disarm or risk military attack.