Foreign Secretary Margaret Beckett has called for a public debate on renewing the UK's Trident nuclear deterrent.
Trident will be decommissioned in about 20 years' time
Mrs Beckett said in an interview with the Sunday Times it was important to ask "do we go on with this?"
Some Labour MPs have accused ministers of trying to stifle discussion about plans to replace Trident - which are estimated to cost up to £25bn.
An announcement on Trident, set to be decommissioned in about 20 years' time, is expected before the next election.
Mrs Beckett told the newspaper proposals to replace Trident would be considered from "first principles".
Tony Blair has said a nuclear deterrent is "essential" and his would-be successor as Labour leader, Gordon Brown, has expressed his commitment to replacing Trident.
The foreign secretary said a White Paper would be published soon as the basis for a debate.
"Obviously whenever you look at these issues the question is 'do we go on with this?'," she said.
"And, if we do, in what way? And why? And what are the issues the government is taking into account when they are considering what their decision should be?"
However Mrs Beckett did not commit to a Commons vote, which is being sought by some MPs.
'Waste of resources'
Work and Pensions Secretary John Hutton said he favoured both Trident and a debate.
"There is no case at all for Britain to take a unilateral act to disarm ourselves," he said.
Labour MP John McDonnell, who has said he will run for the Labour leadership, told BBC One's Sunday AM programme the cost of replacing Trident could be up to £76bn.
"I think that is a waste of resources on a weapon we would never use and wouldn't defend us even," he said.
Shadow Defence Secretary Liam Fox said an urgent debate in the Commons was needed.
"We are committed to retaining a nuclear deterrent as long as a nuclear threat remains," he said.
"At a time when rogue states are developing nuclear weapons it is not the time to drop our guard."