"We are not asking for nuclear weapons to be given to us," Zelensky told journalists, a few days after suggesting Kyiv would seek either NATO membership or nuclear arms.

Ukraine inherited the world's third-largest nuclear arsenal when the Soviet Union broke up in 1991. It surrendered the weapons three years later after receiving security guarantees from Russia and the United States.

The security guarantees, known as the Budapest Memorandum, required that the signatories respect Ukraine and the other ex-Soviet republics' territorial integrity and independence.

"We gave away nuclear weapons. We did not get NATO," Zelensky said in the comments to journalists late Monday that were released under embargo. "All we got was a full-scale war and many victims, so today we have only one way out."

"We need NATO, because we don't have the weapons that can stop Putin," he added.

He was clarifying comments made at a EU summit last week when he said "either Ukraine will have nuclear weapons, which will protect us, or we must have some kind of alliance."

The remarks triggered anger in Moscow.

"This is a dangerous provocation," Russia's Vladimir Putin said told journalists ahead of the BRICS summit in Kazan. "Any step in this direction will be met with a corresponding reaction," he warned.