"Russia has earlier used military force against its neighbors, Georgia, Ukraine and others, so the threat is real and engaging in dialogue is important in finding a political solution," NATO Secretary-General Jens Stoltenberg told CBS.
He said the alliance should be prepared for Russia to possibly use force again.
"At the same time, we must be prepared as Russia may use force again. We must send a clear message that if Russia does so, it will have severe economic and political consequences.
"We need to understand that Russia is aggressor, Russia has occupied Crimea, they support separatists in Donbas, eastern Ukraine and carry out cyber attacks against Ukraine," Stoltenberg said.
He reiterated that the Alliance would not compromise on the basic principles of European security.
"NATO allies can not compromise on the basic principles of European security, the principles of international security, that every country has the right to choose its own path, to decide for itself whether it wants to join NATO," - said the Secretary General.