Home secretary Theresa May has said Trident should be renewed as soon as possible, calling for a parliamentary vote before the summer recess.
May, the Tory leadership favourite, said that it is necessary to renew the submarines to confront an insecure world, pointing particularly to the risk posed by Russia, as well as North Korea.
The summer recess starts on 21 July.
Writing in the Daily Mail, May appealed to voters by stating she has experience of dealing with threats to national security.
She wrote: "While it is true that the terrorist threat we face has grown more serious, it does not mean we no longer face a threat from conventional enemies in the forms of other nation states.
We have all witnessed the renewed belligerence of Russia in recent years, most notoriously in the case of its illegal annexation of Crimea, and Vladimir Putin is intent upon upgrading Russia's nuclear forces.
In the face of such strong evidence, it would be sheer madness to contemplate even for a moment giving up Britain's independent nuclear deterrent. And there is no room for compromise, and no room for cheese paring.
"We need a full fleet of four submarines, capable between them of providing what the military call ‘Continuous At Sea Deterrence’, or permanent, around-the-clock cover.
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"A lot of parliamentary business has, for obvious reasons, been put on hold until the leadership election is complete and a new prime minister is in post.
"But when it comes to the nuclear deterrent, the national interest is clear, the Conservatives are united, and we have waited long enough," she added
Labour is split on the renewal of Trident, with leader Jeremy Corbyn a pacificist and opponent.
Meanwhile, the Conservative leadership race proper gets underway this morning, as the 330 Tory MPs will vote.
The ballot box will open at 11am, closing at 6pm, with a result expected at 7pm. The candidate with the least votes will be eliminated.