Nicola Sturgeon is to update MSPs on Brexit and her plans for a possible Scottish independence referendum in a long-awaited speech at Holyrood.
The Scottish first minister will make a statement on “Brexit and Scotland’s future” at Holyrood from 13:30.
BBC Scotland understands that she will not announce a specific date for a further vote on independence.
Her spokesman said she would “strike an inclusive tone” while “setting out a path forward for Scotland”.
But the Scottish Conservatives said Ms Sturgeon was “obsessed” by independence and was neglecting other issues.
Labour and the Lib Dems also hit out in advance of the statement, while the Greens urged Ms Sturgeon to “fire the starting gun” on a new independence vote as an “escape route from Brexit”.
The statement comes days before the SNP conference, which is set to be dominated by discussion of the party’s “growth commission” paper of plans for independence.
Ms Sturgeon called for a second referendum on Scotland’s relationship with the EU immediately after the Brexit vote in 2016, but put her plans on hold after the snap general election the following year.
At that point, she said she would come back and update MSPs on the “precise timescale” for the new vote – known as “indyref2” – once there was more clarity about the outcome of Brexit negotiations.
But BBC Scotland’s political editor Brian Taylor understands she will not set out a specific referendum date in her latest statement.
“Instead, she’ll set out steps to protect her existing referendum mandate, leaving open the prospect of a ballot before the next Holyrood elections in 2021,” he said.
“The first minister hopes her statement will content SNP activists ahead of the party conference this coming weekend.”
The first minister’s official spokesman said Wednesday’s 30 minute statement would “explore some of the issues that have arisen as a result of the ongoing Brexit situation and Scotland’s constitutional future”.
He said: “It will be a detailed and substantive statement setting out a path forward for Scotland amid the ongoing Brexit confusion at Westminster.
“The first minister will take time to set out her thoughts on that front and in doing so she will seek to strike an inclusive tone.”
Analysis by Brian Taylor, BBC Scotland political editor
Of course the SNP conference at the weekend is concentrating minds. There is a restlessness in the independence movement more generally, and there is a restlessness in the SNP.
I was consulting various folk yesterday at Holyrood about their views, and one very senior figure in the party said that the way to placate the conference would be to announce a referendum and announce a date. There’s just one snag – you might not win that particular referendum.
I think the argument here is that Brexit is the potential trigger for a further referendum because Scotland was told in the 2014 independence referendum that the way to stay in the EU was to stay in the UK. That proved not to be the case.
But the offer of independence has always in Scotland been predicated upon having the confidence to take charge of one’s own affairs, and the other thing that Brexit does is it knocks the confidence of the nation.
There is a pro-independence majority at Holyrood, between the Greens and the SNP, which saw the parliament back calls for a new referendum in March 2017.
Green co-convener Patrick Harvie said it would be “hugely disappointing” if the SNP let the mandate to hold a second referendum within the current Holyrood term expire “in the face of Tory obstructionism”.
He added: “Scotland needs an escape route from a Brexit it didn’t vote for and the Scottish Greens stand ready to campaign hard for an independent Scotland in the EU.”
The UK government has said it would not give its backing to a new referendum via a “section 30 order” like the one which underpinned the 2014 vote.
Ms Sturgeon told MSPs in March that “the legal basis of any future referendum should be the same as the referendum in 2014, which is the transfer of power under a section 30 order”, but said the “anti-democratic” Conservatives were “running scared of the will of the Scottish people”.
Holyrood’s other parties all oppose independence, and spoke out ahead of the first minister’s statement.
Scottish Conservative interim leader Jackson Carlaw said Ms Sturgeon was “passing up the opportunity” to talk about topics such as education to instead focus on “her real priority – her plan for a divisive second referendum on independence”.
He said: “The only reason this statement is happening at all is because Nicola Sturgeon put a second independence referendum back on the table following the EU vote – and she has obsessed about it ever since.
“All this keeps open the divisions from the 2014 referendum – and leaves us with less time spent focusing on getting Scotland’s economy growing again.”
Scottish Labour leader Richard Leonard said there was “no evidence that the people of Scotland want another independence referendum”.
He added: “The mess of Brexit throws into sharp relief the challenges of leaving a political and economic union. The answer to challenges of the UK leaving the EU is not and never will be Scotland leaving the UK.”
And Scottish Lib Dem leader Willie Rennie urged Ms Sturgeon to “tell parliament she has learned the lesson of Brexit, that breaking up long-term economic partnerships is damaging and divisive and that she does not want to inflict that on Scotland with independence”.