• UN head Antonio Guterres warned on the same day that humanity was 'just one miscalculation away from nuclear annihilation'
• The Russian president put Russia's nuclear arsenal on high alert in February
• State-TV pundits in Russia suggested using nuclear weapons against the UK

Vladimir Putin has said a nuclear war must 'never be started' following heightened tension between Moscow and NATO in light of Russia's invasion of Ukraine.

'As a state party to the Non-Proliferation Treaty and one of its depositaries, Russia is consistently complying with the letter and the spirit of the Treaty,' Putin said in a letter to participants of a conference on the treaty in New York.

'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.'

UN head Antonio Guterres warned on the same day that humanity was 'just one miscalculation away from nuclear annihilation,' with the world facing a threat 'not seen since the height of the Cold War.'

'We have been extraordinarily lucky so far. But luck is not a strategy. Nor is it a shield from geopolitical tensions boiling over into nuclear conflict,' Guterres said at the start of a conference of countries belonging to the nuclear Non-Proliferation Treaty.

China, Russia, Britain, the United States and France have agreed that a further spread of nuclear arms and a nuclear war should be avoided, according to a joint statement by the five nuclear states on the UN Security Council, published by the Kremlin on Monday.

The United States and its nuclear allies also rebuked Russia for 'irresponsible and dangerous' talk about possibly deploying nuclear weapons as a review of the keystone nuclear treaty opened at the United Nations.

'Following Russia's unprovoked and unlawful war of aggression against Ukraine, we call on Russia to cease its irresponsible and dangerous nuclear rhetoric and behavior, to uphold its international commitments,' said the United States, France and Britain in a statement.

'Nuclear weapons, for as long as they exist, should serve defensive purposes, deter aggression, and prevent war. We condemn those who would use or threaten to use nuclear weapons for military coercion, intimidation, and blackmail,' they said.

The call was issued as leaders met at the United Nations in New York for the 10th review conference of the Treaty on the Non-Proliferation of Nuclear Weapons (NPT), which came into force in 1970.

It comes as concerns are rising about the spread of nuclear technology, especially in Iran and North Korea, and China's rapid expansion of its nuclear arsenal.

While five leading nuclear powers are among the 191 states party to the pact, India, Pakistan, Israel and North Korea are not.