The crackdown in Catalonia looms large over the Scottish National Party's annual conference that opens Sunday, where the leadership is under pressure from some members to address Scotland's own independence ambitions.

Scottish independence is not on the agenda of the three-day conference after the SNP's First Minister Nicola Sturgeon formally shelved plans until Brexit negotiations advance.

But some party members are disgruntled and an SNP source said he expected an emergency motion on Catalonia, where some separatist leaders are calling for a declaration of independence from the rest of Spain this week.

"There will be an emergency resolution on the events in Catalonia, which means there will be some opportunity for (Scottish independence) to be mentioned," the source told AFP.

Former SNP lawmaker Kenny MacAskill said the crackdown by Spanish police in Catalonia and Britain's failure to condemn it would fuel Scotland's own separatist ambitions.

"For SNP members, the failure of UK parties to properly condemn what happened in Catalonia further justifies the case for Scottish independence," he told the Herald daily.

Sturgeon has voiced concern over the situation in Catalonia but the SNP leadership is not keen to be seen as supporting an independence bid ruled unconstitutional by Spain's government and courts.

However, she told BBC television on Sunday: "You can't simply, in a democracy, say there is no legal and legitimate way for people to decide what they want their future to be -- that would be an absurd position."

- 'Premature' to set a date -

The SNP lost an independence referendum in 2014 in which 55 percent voted to remain part of Britain.

But in the aftermath of Britain's vote to leave the European Union last year, Sturgeon argued that another independence referendum was needed as pro-EU Scotland would be dragged out against its will.

Sixty-two percent of Scots opted to stay in the EU but Britain as a whole backed Brexit by 52 percent.

Conservative Prime Minister Theresa May dented the nationalist advance when her unionist party won back 12 seats in Scotland in a snap general election in June.

But Sturgeon insisted Sunday that she still had a mandate to call another independence vote and pointed to divisions in May's government over Brexit and the stalled negotiations with Brussels.

"As people look ahead and see the damage likely to be done by this unfolding disaster that is not just Brexit but this incompetent, chaotic approach to Brexit being presided over by Theresa May... then the case for Scotland's future being in Scotland's hands... becomes greater and stronger by the day," she told the BBC.

However, she repeated that it would be "premature" to set a date now, saying she would wait until the terms of Britain's withdrawal from the EU become clearer.

- Clock is ticking -

A majority of Scottish lawmakers currently favour leaving the United Kingdom, but that could change at the next Scottish parliament election in 2021 -- so the clock is ticking for the SNP.

Kirsty Hughes, director of the Scottish Centre on European Relations, said a "possibility" could be a vote after Britain's departure from the EU in March 2019 and before the 2021 vote at Holyrood.

But she warned: "There is a strong view that if you have a second independence referendum you can't afford to lose it, because then it really is over and done with."

Kevin Pringle, a former SNP strategic communications director, said another referendum before 2021 was "not impossible".

"Yet the likelihood is the SNP will need a fresh mandate, with a renewed Holyrood majority, before the UK government will agree. That's a tall order," he wrote in The Times.

Ian Blackford, the SNP's leader at Westminster, told AFP the party was proceeding cautiously.

"We have come through a period where there have been a lot of elections and referendums in Scotland," he said.

"After the Westminster election, the party has had to reflect a little bit on where we are."

Source: AFP