Anti-Nato activists in the SNP are meeting to urge the party leadership not to ditch its policy of keeping Scotland out of the alliance.
The SNP leadership has put the issue of Nato on the agenda for its autumn conference, with defence spokesman Angus Robertson proposing a motion in favour of inheriting the UK's membership.
Mr Robertson has insisted the motion would not change the SNP's anti-nuclear stance, but some campaigners have accused the party of "buckling" over its pledge to remove the Trident submarines from Scottish waters.
The party's Campaign for Nuclear Disarmament (CND) group is holding a seminar in Glasgow to "educate" nationalists about what the about-turn could mean.
Gareth Finn, SNP CND group convener, said: "The main aim is to educate SNP members about what membership of Nato would look like. I'd like to think they're all anti-nuclear but when it comes to Nato, there's a small number of people that seek to change policy."
The conference is expected to be attended by some MSPs who oppose the proposed change of direction. They include backbenchers Sandra White, John Finnie, Dave Thompson and Jean Urquhart.
The SNP's youth wing has already resolved to oppose the pro-Nato motion, due to be debated at the party's annual conference in October.
First Minister Alex Salmond has said the party remains firmly anti-nuclear and the SNP would seek to "trade in" the nuclear submarines at Faslane if Scotland became independent.
The Trident Ploughshares anti-nuclear group has accused the leadership of showing a "slowly buckling resolve to rid Scotland of nuclear weapons".
A spokesman said: "To join Nato while claiming that you want rid of Trident just does not make any sense: Nato is a nuclear weapons alliance. If your state does not have nuclear weapons, as a member it means you accept that other members of the alliance are ready to use them to commit mass murder on your behalf.
An SNP spokesman said: "SNP members have the democratic opportunity to make their views on Nato membership clear at the annual conference in October, where we are going to have an excellent debate on defence policy, including reaffirming the party's strong anti-nuclear stance."