But additional uncertainty comes from the fact that Russia is also due to hold its own nuclear exercises soon, possibly at the same time as Nato or just after, according to Nato diplomats. That could complicate the 30-country military organisation’s reading of the war and of Moscow’s intentions.

02:17

‘Sabotage’ behind gas leaks in Russia’s Nord Stream pipelines, say EU, Nato officials

‘Sabotage’ behind gas leaks in Russia’s Nord Stream pipelines, say EU, Nato officials

“Russia will also be conducting its annual exercise, I think, the week after or just after the annual exercise,” UK Defence Secretary Ben Wallace told reporters. But “what we don’t want is to do things out of routine”.

“This is a routine exercise and it’s all about readiness,” Wallace said, just as “Nato’s meeting is all about making sure we are ready for anything. I mean, that is the job of this alliance, to make sure that the 30 partners together are ready for what is thrown at us. And we have to continue to work at that”.

Meanwhile, Russian missiles pounded more than 40 Ukrainian cities and towns, officials said on Thursday, as the Nato meeting in Brussels unveiled plans to strengthen Europe’s air defences after committing more military aid to Kyiv.

North Korea launches cruise missiles that can carry nuclear weapons

The new pledges prompted Moscow to renew warnings that Western states’ help made them “a direct party to the conflict” and that admitting Ukraine to Western military alliance Nato could trigger World War Three.

“Kyiv is well aware that such a step would mean a guaranteed escalation to a World War Three,” deputy secretary of Russia’s Security Council, Alexander Venediktov, told the state TASS news agency on Thursday as the United States vowed to defend “every inch” of allied territory.

Moscow has repeatedly justified the February 24 invasion that has killed tens of thousands of people in what it calls a “special operation”, by saying Ukraine’s ambitions to join the alliance posed a threat to Russia’s security.

Nato is not likely to quickly allow Ukraine to join, not least because its membership during an ongoing war would put the US and allies into direct conflict with Russia.

Nato’s upcoming nuclear exercise, dubbed “Steadfast Noon”, is held around the same time every year and runs for about one week. It involves fighter jets capable of carrying nuclear warheads but does not involve any live bombs. Conventional jets and surveillance and refuelling aircraft also routinely take part.

Fourteen Nato member countries will be involved, which was planned before Russia’s invasion. The main part of the manoeuvres will be held more than 1,000km (625 miles) from Russia.

Nato does not possess any weapons. The nuclear weapons nominally linked to the alliance remain under the firm control of three member countries – the US, the UK and France. But France insists on maintaining its nuclear independence and does not take part in Nuclear Planning Group meetings.

Earlier this week, Nato Secretary-General Jens Stoltenberg warned that it “would be absolutely the wrong signal to send” if the world’s biggest security organisation were to cancel the manoeuvres.

“Nato’s firm, predictable behaviour, our military strength, is the best way to prevent escalation,” Stoltenberg said. “If we now created the grounds for any misunderstandings, miscalculations in Moscow about our willingness to protect and defend all allies, we would increase the risk of escalation.”

Ukraine accelerates Nato bid following Russian annexation

With the Russian army retreating under the blows of Ukrainian forces armed with Western weapons, Putin raised the stakes by annexing four Ukrainian regions and declaring a partial mobilisation of up to 300,000 reservists to buttress the crumbling front line.

As his war plans have gone awry, Putin has repeatedly signalled that he could resort to nuclear weapons to protect the Russian gains. The threat is also aimed at deterring Nato nations from sending more sophisticated weapons to Ukraine.

Stoltenberg described Putin’s spiralling nuclear rhetoric as “dangerous and reckless” and underlined that the allies “have also conveyed clearly to Russia that it will have severe consequences if they use nuclear weapons in any way”.

At least 15 Nato countries have signed a letter of intent to join a long-term German project to create a European anti-missile shield that would boost protection for much of the continent.

The system will have several layers to intercept various kinds of missiles from different heights and would be fully deployable through Nato.

The 15 countries, which include Germany, “want to jointly tackle this effort to close the gaps in air defence”, German Defence Minister Christine Lambrecht told reporters on the sidelines of the Nato ministerial meeting in Brussels on Thursday.

“It’s about being interoperable, it’s about being able to set prices, it’s about being able to support each other, so it’s a win-win situation for the countries that are part of it.”

Lambrecht pointed to increased security risks in Europe following Russia’s invasion of Ukraine and related threats made by Putin. “We have to move quickly now,” she said. “It’s important that those gaps (in our defence) are closed because we all see in which times we are all living in, these are dangerous and challenging times.”

Lambrecht said other countries may also eventually join the plan, which is still in its early stages. It has to overcome production bottlenecks and delivery delays at many companies in the private sector. “We are open to everyone and know that many countries are interested,” Lambrecht said, adding Germany had already entered into negotiations.

Additional reporting by Bloomberg, Reuters