Scotland's First Minister Nicola Sturgeon says she plans to trigger another independence referendum.
Ms Sturgeon said the vote could be held in autumn 2018 at the earliest.
Speaking at Bute House in Edinburgh she said: "In my view it is important that Scotland is able to exercise the right to choose our own future at a time when the options are clearer than they are now, but before it is too late to decide our own path."
Since the UK vote to leave the European Union, Ms Sturgeon has repeatedly said a second independence referendum is "highly likely".
Scots voted 62% to 38% to remain the EU while the UK as a whole voted to leave.
Ms Sturgeon said: "The timing of the Brexit negotiations are not within the control of the Scottish Government. However, we must plan on the basis of what we do know now and what we know is that on the timetable set out by the Prime Minister, the shape of the Brexit deal will become clear in the autumn of next year ahead of ratification votes by other EU countries.
"That is therefore the earliest point at which a referendum would be appropriate."
Ms Sturgeon had called for Scotland to be given a "differentiated deal'' which would see the country remain part of the European single market through membership of the European Economic Area, but said the UK Government has refused to compromise.
She said Theresa May and the UK Government had been given "every opportunity" to compromise but had "not moved even an inch".
The First Minister said appeals have been met with a "brick wall of intransigence".