Scottish lawmakers on Tuesday begin a two-day debate on First Minister Nicola Sturgeon's call for an independence referendum – a major headache for Prime Minister Theresa May as she prepares to launch Brexit.
The Scottish parliament's vote on Wednesday is widely expected to endorse Sturgeon's campaign to get the British government to agree to a second vote after a 2014 one in which Scots voted to stay in Britain.
The semi-autonomous Scottish government wants to ask the people of Scotland to reconsider their vote against independence with a new referendum before Britain is expected to leave the EU in 2019.
Sturgeon, leader of the ruling Scottish National Party (SNP), intends to use the Edinburgh parliament's voice to assert Scotland's "sovereign right" to choose its own future.
She said her Brexit compromise for Scotland to be allowed to remain in the European single market even as the rest of Britain leaves had been met with "a brick wall of intransigence" in London.
The Scottish parliament cannot hold a legally-binding referendum without London's consent – and Conservative Prime Minister Theresa May has insisted that "now is not the time" for a vote.
But Sturgeon has said it would be "democratically indefensible" to block a referendum, although she has signalled she is willing to negotiate on a date.
"This crucial decision over our future should not be made unilaterally by me, or by the prime minister,” she said.
"It should be made by the people of Scotland, and I call on parliament to give the people that choice."
The SNP does not have an outright majority in Edinburgh, but it has already secured the support of the Green party for another independence bid.
Patrick Harvie, leader of the Greens, said, "I think Theresa May will be taking a huge risk ... if she refuses to acknowledge that we have a right in Scotland to have a say about our future."