MPs will vote early in 2007 on whether Britain's nuclear weapons system should be replaced, Downing Street has said.
The operational end of Trident's life is due to be 2024
Ministers are to outline their favoured option - expected to be a replacement for the Trident system - in a white paper to be published in December.
The vote will follow a three-month consultation on the plans, which were discussed at Thursday's Cabinet.
Ministers want a quick decision to ensure any replacement is ready when Trident's working life ends in 2024.
But Commons leader Jack Straw said "There is no suggestion whatsoever of this decision being rushed."
He added: "We have a responsibility not to cop out of this but to come to a decision, and we shall.
"We're talking about defence of the nation here, not the Shops Act or fox hunting."
TRIDENT MISSILE SYSTEM
Missile length: 44ft (13m)
Weight: 130,000lb (58,500kg)
Diameter: 74 inches (1.9m)
Range: More than 4,600 miles (7,400km)
Power plant: Three stage solid propellant rocket
Cost: £16.8m ($29.1m) per missile
Source: Federation of American Scientists
The white paper would "recite" options and say why they were acceptable or not - and a vote will be held on a single recommendation, Mr Straw said.
Prime Minister Tony Blair and Chancellor Gordon Brown - widely expected to be his successor - have both indicated their support for retaining an independent nuclear weapons system.
Mr Blair has said they were an essential part of Britain's ability to defend itself.
Supporters argue Trident is needed to deter any threat - particularly at a time when countries like North Korea and Iran harbour their own nuclear ambitions.
The Conservatives also back retaining nuclear weapons, while the Liberal Democrats have called for a wider vote on the options.
Liberal Democrat leader Sir Menzies Campbell said: "I have written to the prime minister to emphasise that any vote on a Trident replacement should focus on the options available.
"We owe it to the British people and future generations to have a proper discussion."
Britain has 16 Trident missiles based on each of the four nuclear submarines.
Defence minister Lord Drayson told a Commons committee this week that the white paper would look at whether to keep a submarine-based system or change to a land-based or aircraft-based system.
Campaigners say Trident should be scrapped
MPs on that Commons defence committee, who are looking at the issue, are also considering a "middle way" of overhauling, rather than replacing, the submarine fleet carrying the US-made Trident missiles.
Anti-nuclear campaigners say they fear the government has already decided to go ahead with replacing Trident.
Critics say the cost of replacing Trident - estimated at up to £25bn - would be better spent elsewhere, particularly as nuclear weapons would be useless in the fight against international terrorism.
Kate Hudson, chairman of CND - the Campaign for Nuclear Disarmament - said a white paper could "close down" the wider debate.