So, this is a subtle hint towards the threatening of using nukes, but it's not really a direct threat. This is Putin expressing that he's well aware that NATO's combined military strength outweighs his, but he has a nuclear deterrent. So, pure military strength isn't the only determining factor here. This doesn't read to me to be a strong threat to use a nuke because you have to remember the context. This is about Crimea and the dominoes that will fall if Ukraine joins NATO and Russia doesn't give up their claim to the area. This will lead to war, but that doesn't necessarily mean that it's going to lead to a nuclear war because that would kind of be counterproductive towards settling what's essentially a regional territorial dispute. I'm not saying that it couldn't spiral out of control, but what would they do? Nuke Crimea? That's not in their interests.