President Trump has in a newly published interview with Newsmax explained more about his decision to send a pair of nuclear submarines "closer to Russia" after the "fresh mouth" of former Russian president Dmitry Medvedev - who currently serves deputy chair of the country's Security Council - made reference to atomic apocalypse in written remarks about the Ukraine war and standoff with Washington.

Trump told "Finnerty" show host Rob Finnerty at the White House that his "eyes light up" when nuclear weapons are mentioned, particularly by a Russian official like Medvedev.

"Well, a former president of Russia who's now in charge of one of the most important councils, Medvedev, said some things that were very bad, talking about nuclear."

Trump continued, "And when you mention the word 'nuclear,' you know, my eyes light up and I say, 'We better be careful,' because it's the ultimate threat."

Medvedev had on Thursday posted on Telegram that Trump should recall "his favorite films about the 'walking dead'" and while referencing Soviet Union nuclear strike doctrine.

Trump explained in the new interview, "He shouldn't have said it. He's got a fresh mouth. He's said things in the past, too. And so we always want to be ready. And so I have sent to the region two nuclear submarines. I just want to make sure that his words are only words and nothing more than that."

When asked by the interviewer whether the submarines are in fact now closer to Russia, the US Commander-in-Chief responded:

"They're closer to Russia. Yeah, they're closer to Russia."

The question remains whether these submarines are merely nuclear-powered or nuclear-armed. Certainly the latter scenario would mark a huge and dangerous escalation, and yet the US has always exercised strategic ambiguity in this regard.

It has been longstanding US national security policy to not disclose if a particular sub is deployed with nuclear warheads on board or not. And the reality is that these submarines are in all kinds of locations, and probably pass Russia's shores not infrequently - but their locations are never really known.