Scotland's First Minister Nicola Sturgeon is to seek permission to hold a second independence referendum, as the UK moves closer to triggering the Brexit process.
Ms Sturgeon said she wanted a vote to be held in late 2018 or early 2019, once the terms of Britain's exit from the European Union had become clearer.
The first minister said the move was needed to protect Scottish interests in the wake of the UK voting to leave the EU.
She will ask the Scottish Parliament next Tuesday to request a Section 30 order from Westminster. The order would allow a fresh legally-binding referendum on independence to be held.
UK Prime Minister Theresa May said a second independence referendum would set Scotland on course for "uncertainty and division" and insisted that the majority of people in Scotland did not want another vote on the issue.
"Instead of playing politics with the future of our country, the Scottish government should focus on delivering good government and public services for the people of Scotland. Politics is not a game."
Mrs May has so far avoided saying whether or not she would grant permission.
Scots rejected independence by 55-45 percent in a referendum in September 2014, though the vote energised Scottish politics and support for the Ms Sturgeon's Scottish National Party (SNP) has surged since then.
Brexit bill passes in UK House of Commons
Ms Sturgeon made her demands hours before British MPs passed legislation allowing the Mrs May to formally start the Brexit process.
MPs voted down two amendments put forward by the upper chamber, the House of Lords, allowing the maximum room for manoeuvre in negotiations with the EU.
The upper chamber had wanted the Article 50 to guarantee the rights of EU citizens in the UK and to ensure that parliament had a meaningful vote on an eventual deal.
The bill is being sent back to the House of Lords for debate and approval. The unelected chamber is not expected to fight for their changes a second time.
Scotland at 'hugely important crossroads'
Ms Sturgeon said the people of Scotland must be offered a choice between a "hard Brexit" and becoming an independent country.
The first minister said the UK government had not "moved even an inch in pursuit of compromise and agreement" since the Brexit referendum.
In the 23 June referendum, the an overall 51.9 percent voted in favour of leaving. While a majority of voters in England and Wales chose to leave the EU, 62 percent of Scottish voters opted to stay.
Ms Sturgeon said Scotland stood at a "hugely important crossroads", and insisted she would continue to attempt to reach a compromise with the UK government.
But she added: "I will take the steps necessary now 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 has published proposals which it says would allow Scotland to remain a member of the European single market even if the rest of the UK leaves.
Ms Sturgeon will rely on the pro-independence Scottish Greens to give her plans majority support in the Scottish Parliament.
Patrick Harvie, the party's co-convener, confirmed the Greens would vote in favour of seeking a Section 30 order.
Scottish Conservative leader Ruth Davidson said Ms Sturgeon had been "utterly irresponsible".
Scottish Labour leader Kezia Dugdale said Scotland was divided enough and another referendum would divide them again. But the party's UK leader, Jeremy Corbyn, confirmed that his MPs would not attempt to block a request for a Section 30 order.
- BBC / Reuters