A senior Russian official has warned that Moscow could react to Western sanctions over its attack on Ukraine by opting out of the last remaining nuclear arms pact and freezing Western assets.

Dmitry Medvedev, the deputy head of Russia’s Security Council chaired by President Vladimir Putin, shrugged off a set of crippling sanctions that the United States, the European Union and other allies slapped on Russia as a reflection of Western "political impotence."

In comments posted on his page on Russian social media VKontakte, Medvedev said the sanctions could offer Moscow a pretext for a complete review of its ties with the West, suggesting that Russia could opt out of the New START nuclear arms control treaty that limits the U.S. and Russian nuclear arsenals.

Medvedev also raised the prospect of cutting diplomatic ties with Western countries, saying "there is no particular need in maintaining diplomatic relations" and adding that "we may look at each other in binoculars and gunsights." He pointed at the possibility of freezing Western assets in the country if the West proceeds with threats to freeze Russian assets.