According to Barry M. Blechman, the co-founder of the Stimson Center think tank, Moscow would not respond with military force were Sweden and Finland to join NATO.
"I think they would be very upset and there would be all sorts of threats, but they would not start a war over it,” Blechman told BNS at a seminar held at the International Center for Defense Studies (ICDS) in Tallinn.
“I would not take a position on whether Sweden and Finland should join NATO, but they should not not do it out of fear of a Russian military attack.
"They are sovereign nations and it is their right to ally themselves with whoever they want.
There are also other ways they can cooperate with NATO short of membership, so they have to decide on the best policy.
Blechman said in his answer to a question from BNS on whether Finland and Sweden opting for NATO membership could prompt Russia to start a conflict involving tactical nuclear weapons.
Asked about possible Russian invasion of the Swedish island of Gotland and Russia placing air defence assets there, Blechman said he thinks "something like that would prompt a response from NATO even if Sweden were not a member" of NATO.