Nicola Sturgeon has said she could be willing to push back an independence vote date to around early 2019 but insisted that it must take place before Brexit.
The SNP leader said that she was willing to enter discussions with Prime Minister Theresa May, who has said now is not the time for a new referendum on splitting from the UK.
However she rejected suggestions that it could ultimately be pushed back until well after Brexit, saying that the people of Scotland must have a choice on their future.
"I set out the time frame in which I think it would be fair and reasonable...she said she does not agree with that timescale," she told the Peston on Sunday programme.
"I think it is for her then to say what time scale she thinks would be appropriate and I'm happy to have that discussion within reason."
Ms Sturgeon suggested that she might be willing to put back a vote until around Spring 2019 after conversations with Downing Street to reach a compromise had taken place.
Host Robert Peston suggested that the UK government would bee keen to put back any fresh independence vote until 2021, but Ms Sturgeon that that length of delay would be unacceptable.
"I don't think that is reasonable because by that point Scotland has been taken out of the EU, two years have elapsed.
"Presumably there is divergence opening up between the rules of the European Union and the single market and where the UK is going
"I think it then gets much harder for Scotland to seek a different course."
"But if she's talking in the spring of 2019, a bit later perhaps than I was suggesting, then there may be some room for discussions around that.
"I'm up for a discussion within reason, but this is not a timetable that should be determined by what is convenient for Theresa May any more than it should be determined by what is convenient for me."
Ms Sturgeon made a firm pledge to hold a second vote on independence at the SNP conference, saying that the vote for Brexit meant had fundamentally changed the relationship between Scotland and the UK.
However latest polls suggest that a small majority wish to stay within the union.
Scottish Conservative leader Ruth Davidson today criticised the SNP for using Brexit as a pretext to force another vote against the wishes of the Scottish people.