Analysts say the currency issue is a vulnerability for the independence campaign, while some nationalists outside Mr Salmond's Scottish National party are vocally worried about the limits that keeping the pound would mean for fiscal policy. At any rate, UK ministers say London would be unwilling to agree to such a pact.
Mr Salmond's case for currency union is based on proposals laid out by a committee of economists that includes Nobel laureate Sir Jim Mirrlees – cited by Mr Carney in his Edinburgh speech as a former academic supervisor and a "great influence on the profession".
But Mr Carney's talk of the possible need for fiscal pooling contrasts with the conclusions of Prof Jim Mirrlees and his colleagues, who argue a currency union would require only a joint "sustainability agreement' between London and Edinburgh.
Some in the SNP accept that currency union might involve much greater limits to fiscal policy freedom, but say it would still leave an independent Scotland with far more control over its economic destiny than possible as a devolved part of the UK.
(Read more: UK to make debt pledge ahead of Scotland referendum)
In the interview, Mr Salmond refused to consider a "Plan B" on the currency, warning that refusal by the remaining UK to accept shared use of the Bank of England would free Scotland of any responsibility for the UK debt.
"You've got a negotiation where the UK government will want to persuade the Scottish representatives that they should take on a share of debt which is the legal liability of Her Majesty's Treasury," he said.