MOSCOW — Russia has declared that it no longer considers itself bound by a self-imposed moratorium on the deployment of nuclear-capable intermediate range missiles, a warning that potentially sets the stage for a new arms race as tensions between Moscow and Washington rise again over Ukraine.

Medvedev, who has been trading sharp remarks with US President Donald Trump on social media, made the statement shortly after Russia’s Foreign Ministry announced that the country no longer considers itself bound by the self-imposed ban on deploying such nuclear weapons.