As the party conference seasons opens, Britain's two main opposition parties have signalled their support for the government's efforts in response to the atrocities in the US.

Following the Taliban's total rejection of US demands both the Conservatives and Liberal Democrats have given their support to Tony Blair as military action moves closer to reality.

The Conservatives' new leader, Iain Duncan Smith, said his party would back whatever action the government takes.

"The Opposition continues to be fully supportive of the government. We want the government to continue to give a lead to our allies in Western Europe to stand shoulder to shoulder with the United States," he said.

Menzies Campbell, the Liberal Democrats' shadow foreign secretary, warned of casualties but accepted the government would have to be taken on its word.

"No one should be in any doubt that if British troops are fully engaged alongside US forces there will be a risk of casualties. In the Gulf War, and again in Kosovo, we escaped pretty lightly. But there can be no guarantee that this will be the case this time. The reality is that if British troops are deployed we will have to take the government on trust. The prime minister has some difficult decisions to take, not all of which will be able to be fully explained to the public," he said.

The Lib Dem conference begins on Sunday, with Labour scheduled to begin its annual conference next weekend. No final decision has yet been taken on whether the Labour and Conservative conferences will be amended, shortened or scrapped altogether as a result of likley military action.