Angus Robertson told the Guardian his party’s priority was to protect Scotland’s membership of the European single market, and he was pressing the Prime Minister to offer a special deal to make this possible.
His comments come as Nicola Sturgeon is said to be about to abandon her policy of rejoining the EU immediately after a vote for independence, amid concerns rising Euroscepticism in Scotland could derail her campaign.
Just a day after the Scottish First Minister demanded a second vote on Independence, senior nationalist sources reportedly told the Daily Telegraph that Ms Sturgeon would take a softer line on membership of the EU and instead try to join the European Free Trade Association (EFTA), whose members include Norway and Iceland.
While a bid for full EU membership was on the table it remained unclear if the SNP would win or lose a campaign to break away; two major polls published on the same day claimed different things, with a survey in The Times stating 57 per cent would reject independence and The Scotsman reporting that support for Ms Sturgeon's campaign was at a record high.
However most sources agree that Scots are losing confidence in the European Union.
A quarter of people who voted for independence in 2014 also voted 'Leave' in last year's EU referendum; that is 400,000 voters Ms Sturgeon cannot afford to lose next time around. This has apparently pushed the SNP to pursue a compromise that they hope will please everyone.
Speaking to The Guardian, Mr Robertson said: “There may only be days, may only be weeks, but where all of our efforts are currently focused is trying to convince the UK government to come to a compromise agreement protecting Scotland’s place in Europe.
“If that road runs out and if we have to have that referendum, we will be turning our attention to making sure that we are making the case publicly, intellectually and in every other way so people understand the choice of a hard Tory Brexit Britain or a Scotland able to to maintain its relations with the rest of Europe.”
Mr Robertson indicated that failure to act by the prime minister made the possibility of independence ever more likely.
“If the UK government genuinely believes in a United Kingdom [it must] take the needs, interests, concerns of the different parts of the UK seriously," he said.
“The Tories are boxing themselves into a very dangerous corner. For a party that claims to be a unionist party they are making it very difficult for people in Scotland, who are not traditionally SNP voters, to look to the future of a Tory-run Britain and accepting that as our best way forward.”
But the Scottish Conservatives scorned the SNP's new line, saying their plans had “unravelled within 24 hours” in “total confusion”.
The party suggested the SNP was backtracking on their previous approach, having received little support for their hard line on independence and EU membership.
Ruth Davidson, the Conservative leader in Scotland, said: “These are surreal comments. How can he say the SNP is focused on negotiations with the UK government when Nicola Sturgeon has just broken off those talks to unilaterally declare another divisive referendum on independence?”
In addition to the SNP facing a lack of support for EU membership at home, Theresa May told the Commons on Tuesday that on her visits to Brussels she “did not detect any support” for an independent Scotland being allowed to join the EU.
Meanwhile, Alfonso Dastis, the Spanish foreign minister, has told Ms Sturgeon that Scotland would have to “join the back of the queue” if it wanted EU membership, as Spain is opposed to the break up of the UK.
But as news broke that Ms May is planning to spend the next two weeks touring Wales, Scotland, and Northern Ireland in an attempt to build support for triggering Article 50, Mr Robertson still appeared to pitch Scottish independence as representing the opposite to Brexit.
He said: “One of the things that has made a lot of people change their minds from no in 2014 to yes at the present time are people who are internationally minded, who do want to live in a country that welcomes visitors and people who choose to live in this country that when people come seeking refuge they should be offered refuge.
"So this is about more than our relationship with Europe – it is about our values as a country."
He argued that the choice the pro-independence campaign would offer voters would be not just about Europe but about Scottish values that he said were “frankly outward looking... not narrow-minded and rejecting of refugees and people who have come from other shores”.