The prime minister has so far opposed calls for another referendum, arguing that the 2014 vote was a once-in-a-generation event, and the Scottish Conservatives are campaigning on opposing a second vote.
However, Ms Sturgeon told the Guardian on Sunday that she believed the UK government’s discussions on the matter had moved from opposing a referendum to discussing when and how it should take place.
“If people in Scotland vote for a party saying, ‘when the time is right, there should be an independence referendum’, you cannot stand in the way of that, and I don’t think that is what will happen,” she said.
“People will always challenge that because of what the supposed position of the UK government is,” the SNP leader added.
In an 11-point plan published earlier this year, the SNP said it would announce a referendum through legislation at Holyrood if there was an SNP majority but the UK government had refused to grant a Section 30 order, setting up a battle in the courts.
However, Ms Sturgeon said she was “pretty confident” that a referendum Bill in the Scottish parliament would not be needed.
She added that her “strong preference and intention” was to hold another referendum in the first half of the parliament, up to 2023, but she would be “guided by the realities of Covid”.
Voters rejected a proposal for Scotland to become an independent country in 2014 by 55 per cent to 45 per cent, with the referendum securing the highest voter turnout (84.6 per cent) in the UK since the 1910 general election.
In January, Mr Johnson suggested that there should be a 40-year gap between the first and second Scottish independence referendum – similar to the gap between the referendums on Europe in 1975 and 2016.
“Referendums in my experience, direct experience, in this country are not particularly jolly events,” the prime minister told the BBC’s Andrew Marr Show.
“They don’t have a notably unifying force in the national mood, they should be only once-in-a-generation.”
However, the SNP has argued that Brexit, which a majority of Scottish voters opposed, has renewed the case for independence.
Additional reporting by PA