Prime Minister Tony Blair has told MPs it is "important" the UK maintains its independent nuclear weapons system.
The government has yet to make a decision on Trident's replacement
Lib Dem leader Sir Menzies Campbell asked for an assurance that MPs would have a vote on whether or not to replace the Trident system.
Mr Blair confirmed that a White Paper outlining options would be published this year, adding that he was sure MPs would have a vote on the issue.
The issue is due to be discussed when the Cabinet meets on Thursday.
Mr Blair told Sir Menzies during the Commons question time exchanges: "I'm sure there will be an opportunity to vote on the issue.
"But in the end I expect this is going to be an issue, not so much of process but of where you stand on this particular issue."
Mr Blair has previously promised a full debate before a decision is made, while Chancellor Gordon Brown has also said he wants to keep Britain's "independent nuclear deterrent".
And Commons leader Jack Straw has said there will be a vote on the issue in the Commons, which would amount to an effective veto.
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
Three Cabinet members - Foreign Secretary Margaret Beckett, International Development Secretary Hilary Benn and Northern Ireland Secretary Peter Hain - are said to have concerns about replacing or extending Trident, the Times newspaper reported on Wednesday.
The Conservatives are in favour of maintaining Britain as a nuclear power.
Defence minister Lord Drayson has said the White Paper would discuss whether to replace the current submarine-based missiles with a land-based or aircraft-based system.
It would set out options, including highlighting the government's preferred option.
Critics say the estimated £25bn needed to replace Trident would be better spent on improving public services and boosting pensions.
The Catholic Bishops of England and Wales have urged the government not to replace Trident nuclear weapons.
Bishop of Portsmouth Crispian Hollis said if the UK developed a replacement, the aim of international disarmament would be undermined.
Bishop Hollis said nuclear weapons could never be used because they were "so uniquely destructive" in that they killed indiscriminately - not just combatants.
Although nuclear weapons had not been used in war since World War Two, Bishop Hollis said it was arguable nuclear weapons did not act as a deterrent given the "escalation of surrogate wars going on throughout the world".