Washington would apply "immense pressure" on an independent Scotland to stop it from offloading Britain's nuclear submarines on to England, MPs were told on Tuesday.
The claim was made by retired Lt Col Stuart Crawford, a defence consultant who appeared before the Commons Defence Committee. The MPs are looking at the implications for defence and the Armed Forces in the event of Scotland leaving the UK.
Crawford, who believes "some transition work" has already been undertaken by the Scottish government into how the UK"s armed forces would be carved up, told MPs that if the SNP government decided it no longer wanted nuclear submarines on the Clyde, "immense pressure would be brought on Scotland from Washington not to pursue that policy."
Crawford claimed that there were "all sorts of plans behind the scenes," although neither the UK nor the Scottish government was being particularly open about them.
The SNP has claimed that an independent Scotland would be nuclear-free, but if the Scottish government disowned the nuclear subs based on the Clyde it would cost the remaining UK billions to rehouse them elsewhere.
Crawford's view was shared by Professor Malcolm Chalmers, the highly-respected researcher from the Royal United Services Institute, who expects a trade-off in post-independence negotiations with England where Scotland will retain the nuclear deterrent in exchange for allowing Scots to enlist in English regiments.
"If the Scottish government said it didn't want to become nuclear, the UK government would say, 'Get real, we have needs as well'," he told MPs.
"If a Scottish government were to say it would be reasonable on this nuclear force, then it will be hard for the UK to turn around and say Scottish personnel could serve in our armed forces," he added.
"You would have some sort of negotiation where it would be accepted that it's not up to Scotland whether the UK should unilaterally disarm."
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The UK government recently signed off contracts which pave the way for a possible renewal of the Trident nuclear submarine system, with a final decision to be taken in 2016, potentially two years after a vote for Scottish independence. On the day it was announced the contracts were going ahead, the SNP warned it would oppose the continued presence of "weapons of mass destruction on the Clyde."
Malcolm Chalmers said that defence was one of the most important considerations in the referendum debate, saying it would dominate negotiations if Scotland votes yes in 2014. Yet he said it might be difficult for Scots to get answers before the vote.
"There may be an understandable reluctance in London to reveal negotiating cards," said Chalmers.
"There is also the issue about providing enough information to the Scottish people so they make an informed decision," he went on. "The basics are pretty clear - that it's an inherent part of being an independent state in our world order.
"My own personal view is that defence will be one of the major issues, it's one of the things that distinguishes independence from anything else," he said.
Chalmers said that an independent Scotland would need its own separate Ministry of Defence and Scots needed to consider how much they'd want to spend on creating that. He said Scotland would face a "very difficult transition period, starting with very little."