A review of the cost of replacing the Trident nuclear deterrent will be concluded by the end of July, Defence Secretary Liam Fox has said.
The "value for money" review was a key concession secured by the Liberal Democrats in the coalition agreement with the Tories.
Dr Fox told MPs that developments in Iran and North Korea showed the threat of nuclear proliferation "is something that we shall face in the future" and had not ended along with the Cold War.
In a Commons debate on the strategic defence and security review (SDSR) on 21 June 2010, Dr Fox said the separate study on Trident would be completed before the Commons begins its summer recess at the end of July.
Dr Fox said that although the "Cold War mindset" which had dominated defence issues needed to change, "when I look at what's happening in North Korea, when I look at what's happening in Iran, I can see that the threat of nuclear proliferation is something that we shall face in the future and it is not simply a by-product of the Cold War".
The Tories "remain committed to continuous at-sea deterrence" but the coalition agreement made clear "we are scrutinising the Trident renewal programme to ensure we get value for money".
Dr Fox said: "The value for money study has begun, the SDSR has begun. The value for money study on Trident will be concluded long before the SDSR and I hope that it will be concluded before the summer recess."
On the SDSR, shadow defence secretary Bob Ainsworth said there had already been "big moves" away from Cold War capability but acknowledged the need to go further, saying Labour would also be carrying out a review if they were in power.
"I totally agree that salami-slicing is not the way and that there probably does need to be a step change and therefore there will need to be some very difficult decisions taken," he said.
But he argued that the government had set "a very tight timetable" for the Trident review.
Watch the second part of the debate