More now from Russian deputy foreign minister Sergei Ryabkov, who has warned of "tragic and fatal" consequences if the West underestimates Russia's determination.
Mr Ryabkov said Moscow was ready to stand up for itself "and ensure its own interests in any situation".
"I don't even want to assume that this underestimation could become tragic and fatal," he said, adding the West was confronting a major nuclear power.
"There are different ways to respond to this - rhetorical and practical. We have the resources to convey signals to the West in the field of nuclear deterrence, even in the absence of our opponents' willingness to conduct a sober dialogue. But there is a danger, it cannot be underestimated, that their side may make a mistake. We will try not to," Mr Ryabkov said at a conference in Moscow.
