A replacement of Britain's Trident nuclear deterrent will be delayed, possibly for as long as five years, the government has decided as ministers seek to save billions of pounds from the defence budget.

David Cameron will confirm to MPs today, when he launches the strategic defence and security review, that the irreversible "maingate" decision on replacing Trident will be delayed until after the 2015 election.

Whitehall sources said that the building of the new generation of nuclear submarines will be delayed until the mid 2020s. The decision means that the first of the new generation of nuclear submarines may not be in operation until 2028 or 2029, four to five years after the first Vanguard is due to be withdrawn in 2024. The lives of the Vanguard submarines will be prolonged to fill the gap.

The prime minister will underline the scale of the cuts to the annual £37bn defence budget today when he announces that Britain will be without a carrier strike capability for a decade. HMS Ark Royal will be decommissioned immediately and its Harrier jump jets will be withdrawn.

The Royal Navy will have to wait 10 years until as many as 50 new joint striker aircraft can be launched using the catapult and trap system – "cat and trap" – from the new Prince of Wales aircraft carrier. This will be the second of the new aircraft carriers to be built at a combined cost of £5.9bn. The first aircraft carrier – the Queen Elizabeth – will be in service between 2016-19 as a helicopter carrier before it is mothballed, known as "extended readiness", and possibly sold off.

Cameron told the cabinet that the decision to abandon a carrier strike capability for 10 years – and to put the Queen Elizabeth aircraft carrier into service for just three years – was a very difficult decision. "The prime minister told the cabinet that this was one of the hardest things he has had to grapple with," one source said. Cameron later reassured Barack Obama that Britain would remain a "first rate military power and a robust ally of the US".

Nick Clegg will today visit the Rosyth shipyard, where the new aircraft carriers will be built. Clegg is likely to criticise Gordon Brown for commissioning such large aircraft carriers which could only be cancelled at a prohibitively high cost.

Ministers will also say that the 10-year gap in the carrier strike capability will allow Britain to work closely with the US and France whose carriers can use the "cat and trap" system. One source said: "We want the right capability over the next 40 years. This delay means the Prince of Wales will be inter-operable with the US and the French."

The Trident replacement is not formally part of the defence review which will lead to an 8% cut in the Ministry of Defence's annual £37bn budget between 2011-15. The MoD will also have to address a £38bn "overspend" in its budget over the next 10 years.

A key announcement will have a major impact on the Trident replacement and will set the scene for a delay. Cameron will say that a seventh hunter killer Astute class submarine will be built.

Building a seventh Astute class submarine at the Barrow shipyard will address one of the main problems in delaying Trident. This is the so called "drumbeat" – the need to ensure continual work in a shipyard to avoid highly skilled scientists leaving to work elsewhere.

Cameron will say that the Trident delay will save £750m between 2011-15. The delay in building the replacement for the Vanguard nuclear submarines marks a departure from Labour's plans. The oldest of the four Vanguard submarines was due to be taken out of service in 2024. The first replacement will now be operational between 2027-29, with 2028 the most likely start date.

Cameron is committed to a "continuous at-sea deterrent" which, at the moment, means that one submarine is always on patrol and a second is ready to be launched at a moment's notice. The servicing of the Vanguard submarines will be slowed to prolong their lives.

Kevan Jones, the shadow defence minister, said: "Delaying Trident raises significant issues about whether you will have to take out nuclear capability before its replacement is in place. This is playing fast and loose with the nuclear deterrent in a way that is reckless."

Dr Julian Lewis, a former Tory defence spokesman, said: "What is shocking is that this is clearly designed as some form of appeasement of the Liberal Democrats who are, and always have been, covert unilateralists ... This is in total breach of the pledges given to Conservative MPs that the Trident replacement would go ahead if we backed the creation of the coalition."