British Prime Minister Theresa May on Thursday rejected the Scottish government's call for a second referendum on independence before Britain leaves the EU - but did not entirely rule out a vote.
"Now is not the time," she said, arguing that all of Britain's energies should be put into the forthcoming Brexit negotiations, with the withdrawal process due to begin later this month.
Scottish First Minister Nicola Sturgeon has been sharply critical of May's plan to pull Britain out of Europe's single market, and on Monday said Scots should have a choice whether to follow that path or go it alone.
The Scottish National Party (SNP) leader suggested the referendum could take place between autumn 2018 and spring 2019 - before Britain is expected to leave the EU.
"Right now we should be working together, not pulling apart. We should be working together to get that right deal for Scotland, that right deal for the UK," May said.
"That's my job as prime minister and so for that reason I say to the SNP: now is not the time."
However, the Conservative leader refused repeated questions about when the right time might be, leaving the door open for a vote further in the future.
Sturgeon responded with a string of angry tweets, saying May's refusal was "undemocratic" and proof that "the Tories fear the verdict of the Scottish people".
The Scottish leader will seek approval next Wednesday for a new vote in the devolved Scottish Parliament in Edinburgh, but May's government has the right to block the request.
May said that talking about an independence vote would make it harder to get a good Brexit deal, saying Sturgeon's proposed timetable "wouldn't be fair" to the Scottish people.
"They'd be asked to make a crucial decision without the necessary information, without knowing what the future partnership will be or what the alternative for an independent Scotland would look like," she said.
But Sturgeon hit back that she was not proposing a referendum now, "but when the terms of Brexit (are) clear and before it is too late to choose an alternative path".