​President Volodymyr Zelensky warned that the world should “prepare” for Russian leader Vladimir Putin to use nuclear weapons in his invasion of Ukraine – and urged air-raid shelters and anti-radiation medicine to be readied for the potential calamity.

In an interview with CNN that aired Sunday, Zelensky was asked whether Putin would deploy chemical or nuclear tactical weapons to further his military goals in Ukraine.

“Not only me – all of the world, all of the countries have to be worried because it can be not real information, but it can be truth,” Zelensky told host Jake Tapper in an interview from his presidential office in Kyiv.

“Chemical weapons, they should do it, they could do it, for them the life of the people, nothing. That’s why,” Zelensky said. “We should think not be afraid, not be afraid but be ready. But that is not a question for Ukraine, not only for Ukraine but for all the world, I think.”

​In an interview with Ukrainian media Saturday night, Zelensky warned of the real possibility of a nuclear attack. ​

“We shouldn’t wait for the moment when Russia decides to use nuclear weapons​.​ … We must prepare for that​,” the Ukrainian leader said. ​

“Anti-radiation medicine and air raid shelters would be needed,” he said, ​noting that Russia “can use any weapon, I’m convinced of it​.​”​

The Russian military has experienced a number of setbacks, including having to pull back from the area around Kyiv and its suburbs because of ferocious ​fighting by Ukrainian forces.

Following the retreat, Russia lost its most powerful naval ship, the guided missile cruiser Moskva, when it sank last week in the Black Sea after being hit by a Ukrainian missile attack.

CIA Director William Burns said last week that a desperate Putin, seeing his forces suffer heavy losses at the hands of the Ukrainians, may resort to using nuclear weapons. 

“Given the potential desperation of President Putin and the Russian leadership, given the setbacks that they’ve faced so far, militarily, none of us can take lightly the threat posed by a potential resort to tactical nuclear weapons or low-yield nuclear weapons,” Burns said​ during a speech last Thursday at Georgia Tech University. ​

Russian forces that withdrew from Kyiv have since regrouped and are preparing for a full-scale attack in the Donbas region of eastern Ukraine where Russian-backed militias have been backing separatist groups since the invasion of Crimea in 2014.

Zelensky said that combat, which could be reminiscent of the open field battles from World War II, could “influence” the entire fight for Ukraine and vowed that his forces will not yield. 

“This is why it is very important for us to not allow them, to stand our ground, because this battle … it can influence the course of the whole war,” Zelensky said​ on CNN​.

“Because I don’t trust the Russian military and Russian leadership​. That is why we understand that the fact that we fought them off and they left, and they were running away from Kyiv – from the north, from Chernihiv and from that direction – it doesn’t mean if they are able to capture Donbas, they won’t come further towards Kyiv​,” he said. ​