The Kremlin said on Tuesday that Russia had not abandoned a moratorium on nuclear testing, and dismissed a suggestion by the editor of a state television channel that Moscow should detonate a thermonuclear device in Siberia as a warning to the West.

President Vladimir Putin, who rules the world’s biggest nuclear power, has repeatedly cautioned the West that any attack on Russia could provoke a nuclear response.

The Soviet Union’s last nuclear test took place in 1990. The US’s last nuclear test took place in 1992 and France and China conducted their last nuclear tests in 1996, according to the UN.

The Kremlin said it had not abandoned the moratorium when asked about remarks by Margarita Simonyan, the editor-in-chief of state-funded broadcaster RT, who suggested that Russia should detonate a nuclear bomb over Siberia.

“At present, we have not left the regime of abandoning nuclear tests,” Kremlin spokesman Dmitry Peskov told reporters.

“I don’t think such discussions are possible now from an official point of view,” Peskov said, adding that Simonyan’s words did not “always” reflect Moscow’s official position.

Simonyan said the Ukraine crisis was moving towards a nuclear ultimatum and that the West would not stop until Russia sent a nuclear message.

“A nuclear ultimatum is becoming more and more imminent and more and more impossible to avoid,” Simonyan said. “They will not backpedal unless it is painful for them.” She quipped that such an explosion would render electronic devices useless — and thus make it easier for her to explain to her children why they were not allowed devices such as iPads.