Nicola Sturgeon has said she will be able to make a judgment on whether to back a second referendum on Scottish independence by the end of this year.
The first minister said her decision would be made when the shape of a deal between Britain and the European Union became clear in the autumn.
Her comments come ahead of the publication of a Scottish government assessment on the impact of Brexit.
The UK government has accused the SNP of trying to undermine the Brexit vote.
The SNP delayed plans for a new vote on independence following the loss of 21 MPs in last year’s general election.
Speaking on the BBC’s Andrew Marr Programme, the first minister said that people wanted to see clarity on the future relationship between the UK and Europe.
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She added: “At that point, what I’ve said is that we will look at that and determine at that stage if Scotland should then have the right to choose between whatever that new relationship with the UK is going to be or choosing to be an independent country.”
When asked if the timetable would be between October and the end of 2018, Ms Sturgeon responded: “That’s when I will be able to look at that and make a judgement about what the next appropriate steps are for Scotland, and I will then report that to the Scottish Parliament and to the people of Scotland.”
She was challenged to acknowledge that a decision to hold a second referendum then would not leave enough time for the independence vote before the UK’s planned withdrawal from the EU in March 2019.
Ms Sturgeon said: “We’ll make decisions on timing when we get to that point and look at that.”
Her comments on independence prompted criticism from her political opponents.
Conservative MP John Lamont said: “Yet again, Nicola Sturgeon would rather focus on indyref2 than deal with the crises she has created in both health and education.
“Nicola Sturgeon has no interest in securing a successful Brexit deal, all she cares about is a second independence referendum.”
Ms Sturgeon was speaking as the Scottish government prepares to publish their assessment of the impact of Brexit on the Scottish economy.
The first minister is adamant that Scotland should remain in the European Union single market and customs union after Brexit.
She said she believed that a majority in the House of Commons wanted to stay in the single market, including those in the Labour Party, who needed to “get their act together”.
The paper will detail the potential impact on Scotland’s GDP, trade and its potential to attract talent from out with the country.
However, the UK government has already ruled out remaining part of the market.
The customs union is the European Union’s tariff-free trading area, which imposes the same taxes on imports from certain countries outside the EU.
The single market also includes the free movement of goods, services, capital and people.
The Scottish government’s paper, titled Scotland’s Place in Europe: People, Jobs and Investment, also details what it believes to be the benefits of the continued freedom of movement for workers from the European Union.
The Scottish Conservatives have urged Ms Sturgeon to back UK-wide rules on trade and immigration rather than seeking any separate deal for Scotland.
It follows the results of a UK-wide survey headed up by Sir John Curtice that suggested 59% of voters in Scotland backed an end to freedom of movement.
The UK government called on the Scottish government to work with it for the benefit of the whole of the UK.
Henry VIII powers
A spokesman said: “We are seeking a deal that works for the whole of the UK, that delivers on the result of the EU referendum.
“Rather than trying to undermine the result of a democratic referendum, we urge the Scottish government to work with us to ensure, as we leave the EU, we protect the UK’s vital internal market.
“Scotland trades four times as much with the rest of the UK as it does with the EU, so it is vital that we ensure that market continues unimpeded.”
Meanwhile, Labour has been urged to join a cross-party bid to keep the UK in the single market and customs union.
The SNP, Liberal Democrats, Plaid Cymru and Greens have joined forces to back an amendment to the EU (Withdrawal) Bill when it returns to the Commons this week.
If passed, the move would stop ministers being able to use so-called Henry VIII powers to take Britain out of the single market and customs union.
The move follows a Brexit summit by the leaders of the four parties which Labour refused to attend.