The Kremlin leader made the comment in a letter to participants of a conference on the nuclear non-proliferation treaty (NPT), more than five months into his war on Ukraine.

"We proceed from the fact that there can be no winners in a nuclear war and it should never be unleashed, and we stand for equal and indivisible security for all members of the world community," he said.

His words to the NPT forum appeared aimed at striking a reassuring note and portraying Russia as a responsible nuclear power.

They contrasted with earlier statements by Putin and other Russian politicians that have been interpreted in North America and Europe as implicit nuclear threats.

In a speech on February 24, as he launched the Russian invasion of Ukraine, Putin pointedly referred to Russia's nuclear arsenal and warned outside powers that any attempt to interfere would "lead you to such consequences that you have never encountered in your history".

Days later, he ordered Russia's nuclear forces to be put on high alert.

The world is facing a level of danger from nuclear weapons not seen since the height of the Cold War, UN Secretary General Antonio Guterres said at the start of the NPT conference on Monday.

The NPT is subject to review every five years, and the 10th review was to have taken place in 2020 but was postponed on account of the pandemic.

CIA director William Burns said in April that given the setbacks Russia had suffered in Ukraine, "none of us can take lightly the threat posed by a potential resort to tactical nuclear weapons or low-yield nuclear weapons".

Russia, whose military doctrine allows for the use of nuclear weapons in the event of an existential threat to the Russian state, has accused the US of leading a "proxy war" against it by arming Ukraine and imposing sanctions.

Earlier on Monday, a Russian foreign ministry source questioned the seriousness of comments by US President Joe Biden calling for talks on a nuclear arms control framework to replace a treaty expiring in 2026.

"Is this a serious statement or has the White House website been hacked?" a Russian foreign ministry source told Reuters.

"If this is still a serious intention, with whom exactly do they intend to discuss it?"

The New START Treaty, struck in 2011, obliged the US and Russia to limit deployed intercontinental ballistic missiles, deployed submarine-launched ballistic missiles and deployed heavy bombers equipped for nuclear armaments.

It also put limits on nuclear warheads on those deployed missiles and bombers and the launchers for those missiles.

Both sides reached the central limits of the Treaty by February 5, 2018 and the Treaty has been extended to the end of February 4, 2026.

with DPA

Australian Associated Press