Vladimir Putin has warned of 'the end of civilization' if the US lowers its threshold for using nuclear weapons.
US nuclear weapons policy justifies their use in 'extreme circumstances' such as a nuclear attack on the US or an ally.
But this year the Pentagon completed initial draft plans for several emerging low-yield sea-launched nuclear weapons, raising fears they may be used as standard weapons in battle.
Putin fears this will lower the threshold for using weapons of mass destruction and could lead to disaster.
Speaking at his annual news conference in Moscow on Thursday, he said: 'They want to make small-scale nuclear weapons in order to use them tactically. But lowering the threshold might lead to a global nuclear catastrophe.'
Putin also said the US is pondering the use of non-nuclear ballistic missiles, saying such a missile could be mistaken for a nuclear-tipped one and trigger a global catastrophe.
'If, God forbid, something like that were to happen, it would lead to the end of all civilisation and maybe also the planet,' he said.
Indirectly referencing Donald Trump's administration, he added: 'These are serious questions and it's a real shame that there's a tendency to underestimate them.'
In 2021, a treaty between the US and Russia that reduces their nuclear arsenals will expire and there are currently no talks on re-signing it.
Putin said: 'The international arms-control system is effectively breaking down now.'
In an indirect question to Donald Trump, he added: 'Not interested? Don't need it? Well, alright then. We'll survive with that, we will ensure our security. We know how to do that.'
Putin also pointed at the US intention to withdraw from the 1987 Intermediate-Range Nuclear Forces (INF) Treaty.
He said that if the US puts intermediate-range missiles in Europe, Russia will be forced to take countermeasures.
'[The US] took another step, they left the (Intermediate-range Nuclear Forces) Treaty.'
Putin said that by reacting to this by increasing defences, he is not trying to gain an advantage, but 'aiming to retain balance and to provide for our own safety.'
Also in the session, Putin said Russia's relationship with Britain was deadlocked after the UK accused two Russian agents of poisoning a double agent Sergei Skripal in Salisbury.
'I don't even have anything to say on this,' he said. 'It's good that he wasn't killed... Thank God, Skripal is alive.'
'This politicised, Russophobic approach - it's a reason, simply a reason to organise yet another attack on Russia.
'If there were no Skripals, they would have come up with something else, that's clear to me. There's only one goal: to constrain Russia's growth as a possible competitor, I can see no other goals.'
He also said the Taliban should be taken into account at peace talks on Afghanistan because of the amount of territory they control.
Putin also said that Russia needed to beef up its military base in neighbouring Tajikistan due the situation in Afghanistan.
This article has been adapted from its original source.
© Associated Newspapers Ltd.