The United States is taking Russian President Vladimir Putin's "irresponsible" veiled threat to use nuclear weapons "seriously," a senior US official said Wednesday.

"It's irresponsible rhetoric for a nuclear power to talk that way. But it's not atypical for how he's been talking the last seven months and we take it very seriously," John Kirby, spokesman for the White House's National Security Council, told ABC's "Good Morning America" after Putin said he would use "all available means" to protect Russian territory.

"We're monitoring as best we can — their strategic posture. So if we have to, we can alter ours. We've seen no indication that that's required right now."

Kirby reiterated previous comments by President Joe Biden when asked what the US response would be to Russia reaching for its nuclear arsenal, which analysts speculate could mean detonating a demonstration blast over the Black Sea, using battlefield nuclear warheads to limit the radiation, or ultimately using a larger weapon.

"There'll be severe consequences. Not only will he be that much more of pariah on the world stage, but there'll have to be severe consequences that the international community will have."

Kirby described Putin's order to mobilize an expected 300,000 reservists from around Russia as a sign of weakness.

"It's definitely a sign that he is struggling," Kirby said. "He has suffered tens of thousands of casualties. He has terrible morale, unit cohesion on the battlefield. Command and control has still not been solved. He's got desertion problems and he's forcing the wounded back ingo the fight — so clearly manpower is a problem."

Kirby said "sham" referendums on joining Russia that are being prepared in Russian-invaded areas of Ukraine would not change US policy.

"That is Ukrainian territory. It doesn't matter what sham referendum they put in place," Kirby said. "We're going to continue to support Ukraine with security assistance and other financial aid, as the president said, for as long as it takes."

EU accuses Putin of putting world peace 'in jeopardy'
Brussels (AFP) Sept 21, 2022 –

EU foreign policy chief Josep Borrell on Wednesday accused Russian leader Vladimir Putin of putting world peace "in jeopardy" by threatening to use nuclear weapons over the war in Ukraine.

"Putin's announcement of sham referenda, partial military mobilisation and nuclear blackmail are a grave escalation," Borrell wrote on Twitter.

"Threatening with nuclear weapons is unacceptable and a real danger to all," he said.

The EU's top diplomat added: "the international community must unite preventing such actions. World peace is in jeopardy."

Borrell joined a chorus of condemnation from the West after Putin said Moscow would use "all the means at our disposal to protect Russia and our people" and ordered a partial military mobilisation, following a series of setbacks in Ukraine.

An EU spokesman had earlier said that Putin's announcements, along with a push for votes to annex occupied territories in Ukraine, showed his "desperation" after a series of military setbacks.

"This is just another proof of Putin that he is not interested in peace, that he's interested in escalating his war of aggression," said EU spokesman Peter Stano.

"This is also yet another sign of his desperation with how his aggression is going against Ukraine."

The EU would impose "consequences" on Moscow over the push to justify annexing areas of Ukraine it has occupied, Stano added.

But he refused to give any details, and EU member Hungary has expressed opposition to imposing more sanctions after six waves of unprecedented economic measures against Russia.

European diplomats told AFP that work was underway to come up with a new round of sanctions that could be put to the EU's 27 member states for approval.

The EU has said it will not recognise the "sham, illegal referendums" staged by the Kremlin in Ukraine. Stano said the bloc would continue its support to help Kyiv liberate its territory.

"Ukraine is fighting a justified war of self-defence for the survival of the nation," he said.

The EU has already disbursed 2.5 billion euros ($2.5 billion) for weapons deliveries to Ukraine and is preparing a fresh tranche expected to be worth an additional 500 million euros.