I don’t know if nuclear first-strike capability is possible. We need to determine if an arms race with Russia could lead to our annihilation; and if so, we need to have both countries agree to a freeze on new nuclear weapons (at least if such a freeze is verifiable). There should of course be immediate inspection of any suspected nuclear weapon sites. If Russia doesn’t agree to this — and if any diplomatic gesture such as inviting them to join NATO doesn’t work —then we need to have tougher sanctions than we do at present.
We should also (especially if such a freeze is non-verifiable) consider removing the threat by the prospect of increased trade.