Prime Minister Tony Blair has refused to commit himself to giving MPs a vote on replacing the UK nuclear deterrent.
Trident will be decommissioned in about 20 years' time
He told a committee of senior MPs there would be the "fullest possible" debate. The decision would be taken in a "more open way" than had happened previously.
The government is expected to outline plans to replace the Trident missile system, which some MPs estimate will cost £20bn, before the next election.
"I'm not committing myself to a vote... not ruling it out either," he said.
'Not ruled out'
Mr Blair said Parliament tended to find a way to have a vote on big issues, and said a decision such as this was "not going to just pop out one day".
Asked about when a promised debate on replacing Trident might begin, Mr Blair told the Liaison committee he could be specific yet.
But he did say that by the end of the year "we should have a clear idea of the timeline" for it.
Defence Secretary John Reid said last year that no decision on replacing Trident had been taken.
But he said Labour was committed to keeping Britain's nuclear deterrent.
Trident is expected to be decommissioned in about 20 years' time. The nuclear deterrent system was last updated in 1980.
Last year, a group of writers, led by Nobel Prize winner Harold Pinter, wrote an open letter to MPs saying there was "no legitimate political, military or moral reason" for replacing Trident.