A £31bn project to replace Royal Navy aircraft carriers and fighter planes may be falling "behind schedule", an influential group of MPs has warned.
An artist's impression of one of the new aircraft carriers
This could mean the Royal Navy being forced to keep using outdated equipment at "substantial extra cost", the Defence Select Committee said.
The delay is blamed on the failure to take key investment decisions.
The contracts to build the two aircraft carriers at four UK shipyards were only announced last week.
The carriers, which are due to enter service in 2012 and 2015, would provide a decade's work for Rosyth dockyard in Fife and BAE Systems' shipyards on the Clyde, Barrow-in-Furness and Portsmouth.
Defence Secretary John Reid said at the time that 10,000 jobs would be created by the work.
The MPs fear the UK may have to consider scrapping its order with US suppliers for 150 new carrier-based strike aircraft if agreement cannot be reached allowing the Navy to operate and service the jets independently.
"It is possible that neither the carriers nor the aircraft will be delivered on time or, crucially, at the same time," the cross-party Defence Committee says in a report.
Chairman James Arbuthnot said the procurement was designed to "provide the Royal Navy with a key capability for the future".
"Unfortunately, as with many other defence equipment programmes, our armed forces are likely to receive the equipment they need and the capability they require to undertake their roles, later than originally planned.
"The Royal Navy may well be forced to run on less capable equipment, beyond the date when it was due to be withdrawn from service."
On the deal with the US on the fighter jets, the MPs called for "cast iron assurances".
"If such assurances are not obtained, the UK might have to consider whether to continue in the programme," said Mr Arbuthnot.