Nicola Sturgeon has warned "Scotland's referendum must be made in Scotland" as her row with Theresa May over a second independence vote escalates.
The First Minister, speaking after a cabinet meeting, said: "There should be no strings attached, no blocking mechanisms applied and no Downing Street diktat."
But Ms Sturgeon also indicated that she could delay another referendum until after Brexit.
On Monday, she said that the vote must take place before the UK leaves the EU in March 2019, but on Tuesday suggested it could place "shortly afterwards".
"The vote must take place within a time frame to allow an informed choice to be made - when the terms of Brexit are clear but before the UK leaves the European Union or shortly afterwards," she said.
"In that way, with the vote taking place between the autumn of 2018 and the spring of 2019, the independence prospectus which we will offer people can be contrasted directly with the Brexit deal which the UK Government will have negotiated by the start of that period."
The Scottish government at Holyrood is likely to debate and vote in favour of a second ballot next Tuesday and Wednesday.
Following a vote, Westminster needs to issue a section 30 order giving Holyrood the legal authority to stage a referendum, leading then to formal talks between both governments on the timing of the vote.
Downing Street, which thinks the referendum should not happen, is likely to want to influence the votes timings and parameters.
Ms Sturgeon made the comments after the Prime Minister accused the SNP of "playing politics with the future of our country" and a vote would lead to "more uncertainty and division".
Theresa May insisted she had been "working closely" with the Scottish government on preparations for Brexit, which was met with jeers from the Scottish Nationalist benches.
Speaking in the House of Commons, she said: "This is not a moment to play politics or create uncertainty.
"It is a moment to bring our country together, to honour the will of the British people and to shape for them a better, brighter future and a better Britain."