The last referendum saw Scots voting 55% to stay in the UK
Scotland's First Minister Nicola Sturgeon says she plans to seek approval next week for a second independence referendum.
She was making a speech ahead of the expected triggering of Article 50, for Brtain to leave the European Union.
"We will be frank about the challenges we face and clear about the opportunities independence will give us", she said from Bute House in Edinburgh.
"Whatever path we take, it should be one decided by us, not for us. So let me set out the plan I intend to pursue.
"First, I will continue to stand up for Scotland's interests during the process of Brexit negotiations.
"Second, I will now take the steps necessary to make sure that Scotland will have a choice at the end of this process.
"A choice of whether to follow the UK to a hard Brexit - or to become an independent country, able to secure a real partnership of equals with the rest of the UK and our own relationship with Europe.
"The Scottish Government's mandate for offering this choice is beyond doubt."
She also says she expects the vote would be held between the autumn of 2018 and the spring of 2019.
Ms Sturgeon added: "Now let me stress, even at this late stage, I am not turning my back on further discussions should the UK government change its mind and decide it is willing to agree to our compromise proposals.
"And, in any event, I will do everything I can to ensure that Scotland's interests are represented in the EU negotiations that lie ahead.
"But I cannot pretend to the Scottish people that a compromise agreement looks remotely likely, given the hardline response from the Prime Minister (Theresa May) so far.
"That means I have to decide on the best plan to protect our interests now."
Ms Sturgeon confirmed she will seek the authority of the Scottish Parliament next week to agree the details of a section 30 order - the procedure that will enable it to legislate for the referendum.
Scottish Conservative leader Ruth Davidson tweeted: "Nicola Sturgeon has today chosen the path of further division and uncertainty. We will vote against any request for a Section 30 next week."
Nicola Sturgeon has today chosen the path of further division and uncertainty. We will vote against any request for a Section 30 next week.— Ruth Davidson (@RuthDavidsonMSP) March 13, 2017
A spokesman for British Prime Minister Theresa May said: "Another referendum would be divisive and cause huge economic uncertainty at the worst possible time."
While UK Labour leader Jeremy Corbyn said it was "wrong to hold another (referendum) so soon" and that the party opposed independence.
However, he added that Labour would not block a second referendum if the Scottish Parliament votes for it.
Westminster and the Scottish Parliament both have to approve a second referendum for it to take place.
The Scottish National Party (SNP) 2015 manifesto opposed the Brexit vote and said 330,000 Scottish jobs were dependent on being in the EU.
The last referendum in September 2014 resulted in Scots voting by 55% to 45% in favour of remaining in the United Kingdom.
Scotland voted by 62% to 38% to remain in Europe during the Brexit referendum campaign.
A poll in September 2016 revealed 50% of Scottish people were actually opposed to a second referendum.
The survey from YouGov found 37% of Scots backed a second vote, while 50% were against.
If a second vote was to be held, the results looked almost identical to last time - with 54% against independence and 46% in favour.
Additional reporting: IRN