NATO “would respond” if Russian President Vladimir Putin uses chemical weapons in Ukraine, US President Joe Biden has said.
Asked if the alliance would take military action, Mr Biden said such an attack “would trigger a response in kind”.
Speaking after meetings of NATO and the G7, he said: “We would respond. We would respond if he uses it [chemical weapons].
“The nature of the response would depend on the nature of the use.”
Russia’s deputy UN ambassador, Dmitry Polyanskiy, had told Sky News Moscow would use nuclear weapons if ‘provoked’ by NATO.
He gave the warning after Vladimir Putin’s spokesman refused to rule out nuking Ukraine in the face of an ‘existential threat’.
Asked if Putin was right to hold the prospect of nuclear war over the rest of the world, Mr Polyanskiy told Sky News: “If Russia is provoked by NATO, if Russia is attacked by NATO, why not, we are a nuclear power.
“I don’t think it’s the right thing to be saying. But it’s not the right thing to threaten Russia and to try to interfere.
“So, when you’re dealing with a nuclear power, of course, you have to calculate all the possible outcomes of your behaviour.”
Chemical warfare is ‘a real threat’ right now, Joe Biden says, as diplomatic talks continue.
The US and its allies have previously said they are concerned Russia might resort to using chemical weapons as its invasion struggles against Ukrainian resistance, with Mr Biden saying it was a “real threat”.
Addressing what would happen if Mr Putin deployed weapons of mass destruction, UK Prime Minister Boris Johnson said: “You have to have a bit of ambiguity about your response, but I think it would be catastrophic for him if he were to do that, and I think that he understands that.”
But he said Mr Biden was right to warn about the threat, adding: “When the Russians start doing stuff about ‘there are factories in Ukraine producing American biological weapons’, you know that is a prelude to a false flag operation.”
NATO Secretary General Jens Stoltenberg echoed his comments, saying: “We are concerned partly because we see the rhetoric and we see that Russia is trying to create some kind of pretext accusing Ukraine, the United States and NATO allies of preparing to use chemical and biological weapons.
“And we have seen before that this way of accusing others is actually a way to try create a pretext to do the same themselves.”
A similar tactic has been used in Syria, where the Russia-backed regime has often sought to blame the rebels it is fighting when it has been accused of using chemical weapons against its own people.
Mr Stoltenberg said if chemical agents were used they could spread across the border, affecting one of its member states.
NATO leaders also agreed to send Ukraine protective equipment to defend itself against biological, chemical and nuclear attacks.
The White House has set up a team of national security officials to plan for what happens if Russia uses chemical or biological weapons in Ukraine, a senior administration official said.
White House national security adviser Jake Sullivan sent a memo 28 February describing how the so-called “Tiger Team” would consider what could happen over the next three months of conflict, the official told NBC News.
Scenarios under discussion were said to have included: Russia using chemical or biological weapons; Russia targeting US convoys carrying weapons to Ukraine; the global food supply being disrupted; and the refugee crisis.
Russia is among 193 countries that have signed the Chemical Weapons Convention, a treaty that bans their development, production or use.
