MOSCOW, Feb 26 (Reuters) - President Vladimir Putin cast the confrontation with the West over the Ukraine war as an existential battle for the survival of Russia and the Russian people - and said he was forced to take into account NATO's nuclear capabilities. The United States has denied that it wants to destroy Russia, while President Joe Biden has warned that a conflict between Russia and NATO could trigger World War Three, though he has also said Putin should not remain in power. "In today's conditions, when all the leading NATO countries have declared their main goal as inflicting a strategic defeat on us, so that our people suffer as they say, how can we ignore their nuclear capabilities in these conditions?" Putin said