Sturgeon: Autumn 2018 'common sense' for indyref2
Scotland's first minister has said autumn 2018 would be a "common sense" date for any second independence referendum.
Nicola Sturgeon continued to insist, however, that no final decision had yet been made on holding such a vote.
In a BBC interview, she said she would take things forward at "the pace that I think is right for the country".
UK government minister Michael Fallon said there was "no need" for a second referendum on the issue.
However, Ms Sturgeon believed another ballot was "highly likely" following last year's UK-wide vote for Brexit which was backed by 52% of the electorate who went to the polls.
In Scotland, 62% of the voting public wanted the UK to retain its EU membership.
Since the Brexit vote, the Scottish government has argued that continuing access to the single market was vital to the country's interests.
Scottish ministers have put forward proposals they claim could achieve this, but have accused the UK government of "intransigence" on the issue.
SNP economic spokesman Stewart Hosie told BBC Breakfast: "The key thing is will the UK government really embark on this hard Tory, cliff-edge Brexit - and we fear they will.
"And secondly, will they actually accept, into the UK negotiated position, the very sensible suggestion put forward by Nicola Sturgeon... if they reject it out of hand then, as the First Minister has said previously, it does make a second independence referendum more likely."
He also agreed with Ms Sturgeon that autumn 2018 "might make sense".
In a recent speech in Edinburgh, Ms Sturgeon said a second independence referendum may become a "necessary" way of protecting Scotland's interests in light of Brexit.
Interviewed by BBC political editor Laura Kuenssberg for a BBC documentary to be broadcast on Thursday, she gave her clearest indication yet about the possible timing of such a vote.
Asked if autumn 2018 was a likely date, she replied: "Within that window, of when the outline of a UK deal becomes clear and the UK exiting the EU, I think would be common sense time for Scotland to have that choice, if that is the road we choose to go down."
Asked if that meant she was not ruling out autumn 2018 as a possible date, she said: "I'm not ruling anything out, I'm going to continue to take things forward at the pace that I think is right for the country."
Analysis by BBC political editor Laura Kuenssberg
At Westminster and Holyrood in recent months there's been a building sense that Nicola Sturgeon has made up her mind to call a vote.
If she is now willing to discuss the timing of a second vote in public, consideration of another independence referendum is far beyond the hypothetical.
The crucial facet of that calculation is that the SNP believes its best chance of winning is before the EU negotiations are complete.
But also, it's up to the Westminster government to permit another referendum. There are huge risks for them in denying it, but ministers in London certainly would not grant a vote at the time of the SNP's choosing without a fight.
Scotland voted to stay part of the UK by 55% to 45% in the 2014 independence referendum.
The most recent polling, by STV, has suggested 50% of voters in Scotland would back Scottish independence.
The Ipsos MORI survey spoke to 1,029 people in Scotland, aged 16 and over, by telephone between 24 February and 6 March.
Ms Sturgeon's predecessor as first minister, Alex Salmond, has already predicted that a second independence referendum would take place in autumn next year.
While the SNP does not hold an overall majority at Holyrood, it could count on the support of the Scottish Greens if the Scottish Parliament voted on holding a new poll.
Permission for that, however, would have to be granted by the UK government at Westminster.
Prime Minister Theresa May has so far declined to be drawn on whether her government would allow a second referendum.
'Attempt to sow division'
Speaking to BBC Radio Scotland's Good Morning Scotland programme, Defence Secretary Mr Fallon said: "Brexit negotiations haven't started yet and they are going to be complex.
"I have seen estimates that they might last for a couple of years, so I can't comment on what might be known in autumn 2018.
"But let me be very clear we don't see any need for another referendum we had one just two-and-a-half years ago, it was accepted as a clear cut result at the time and there is plenty of other business for the Scottish government to be getting on with."
Responding to Ms Sturgeon's BBC interview, Scottish Labour leader Kezia Dugdale said: "This is yet another attempt by Nicola Sturgeon to sow division and uncertainty, at a time when the country needs to pull together more than ever.
"The first minister has been all over the place - one week she threatens a vote, the next week she backs away from one. All this does is cause even more uncertainty for Scotland's economy at a time when businesses are already struggling as a result of the Tories' plans for a hard Brexit.
"Nicola Sturgeon could provide much needed clarity on Scotland's future by ruling out another independence referendum altogether."
Nicola Sturgeon's interview was recorded for the BBC documentary Brexit: Britain's Biggest Deal - to be broadcast on BBC Two in England, Wales and Northern Ireland at 21:00 and on BBC Two Scotland at 23:15 on Thursday.