While the government officially says no decision has been made on a replacement for Trident, military experts believe the programme could prolong the life of the UK's ultimate deterrent by up to ten years.
That could mean at least a further 30 years of service for the nuclear submarine and missile bases on the Clyde.
"The actual hardware side of this is not going to change until they have a new submarine or a new missile," said Tim Ripley, research associate at the Centre for Defence and International Studies in Henley. "In terms of where they berth the subs at Faslane, or store the missiles at Coulport, [that] will not change. The actual part of the weapons system affected by this is no bigger than the engine of a car."
The Atomic Weapons Establishment at Aldermaston is believed to be working with the Americans on a project known as the Reliable Replacement Warhead (RRW). It would be a simpler device that could be tested in a laboratory rather than with a full-scale detonation, which would break international law against nuclear testing.
"The government haven't owned up publicly to being part of the American warhead programme," said Mr Ripley. "That is still a question mark, although it is a strong possibility. Aldermaston has hired new scientists and is co-operating with the Americans, so it's plausible."
He said the RRW is essentially "21st century electronics meets established nuclear physics", and would not change the operation of Trident.
"It's like upgrading your PC; the new hard drive and software doesn't change the size of the box," he said. "The implication is: does this keep Trident in service for longer and put off the day when they have to bite the bullet and go for a replacement?"