

Nato, in an echo of the cold war, is preparing to re-evaluate its nuclear weapons strategy in response to growing tension with Russia over Ukraine, sources at the organisation have said.

Updating Nato’s nuclear policy would amount to an escalation in tit-for-tat exchanges with Russia since the Ukraine crisis erupted last year. Expressing concern over President Vladimir Putin’s announcement last week that Russia was to buy 40 new intercontinental ballistic missiles, Nato officials also said there was alarm over Russian rhetoric on nuclear weapons and the extent to which such weapons are involved in military exercises.

A Nato diplomat said: “There is very real concern about the way in which Russia publicly bandies around nuclear stuff. So there are quite a lot of deliberations in the alliance about nuclear [weapons], but it is being done very slowly and deliberately. We need to do due diligence on where we are.”

The issue is being discussed on the margins of a two-day Nato ministerial meeting that began in Brussels on Wednesday. But the US is keen to get the issue on the table and a meeting of Nato’s ministerial nuclear planning group is likely to be held later this year – earlier than planned – to discuss refreshing the nuclear doctrine.

Among potential topics is an enhanced role for nuclear weapons in Nato military exercises. Also up for discussion would be how to better interpret Russian warnings about nuclear weapons: whether they should be taken seriously or whether these amount to no more than rhetoric.

Speaking on the sidelines of the summit, British defence secretary Michael Fallon said Russia’s “nuclear messaging is not helpful”. He added: “It is important we understand its implications for the alliance”.

Since the peak of the cold war, the US and Russia have slashed their nuclear arsenals but Russia still has an estimated 1,582 strategic warheads deployed on 515 missiles and bombers, while the US has 1,597 deployed on 785. There is no suggestion at Nato headquarters of a return to the days of nuclear arms races and the doctrine of mutually assured destruction, and the US has specifically ruled out returning cruise missiles to Europe.

But Nato officials, military and diplomats are raising worries that the US-led alliance’s existing nuclear posture reflects the thinking of a decade ago when Russia was viewed as a potential partner. That strategy badly needed to be refreshed, they suggested. Although Nato nuclear exercises are classified, the organisation does, like Russia, conduct them. The concern at Nato is that the role of nuclear weapons in such exercises needs to be upgraded to take account of the changed relationship with Moscow.

Nato’s secretary general, Jens Stoltenberg, speaking at a press conference on Wednesday, said the nuclear issue was serious and had to be treated with caution. “The nuclear activities, the investments of Russia in new nuclear capabilities, and the exercise activities by Russia in the nuclear domain is part of the global picture where we see a more assertive Russia.”

The American ambassador to Nato, Douglas Lute, briefing journalists in Brussels on Tuesday, said: “There is a general assessment under way in Washington and a parallel assessment here in Nato to look at all the possible implications of what Russia says about nuclear weapons, its doctrine and so forth, its pronouncements, its rhetoric, and what we actually see on the ground in terms of development and deployment.” Nato, he added, had not yet reached any conclusions or decided on “what are the actions that are implied in our response”.

Putin last week announced plans to purchase 40 intercontinental ballistic missiles and complained of US acts in eastern Europe as amounting to the most aggressive since the cold war. Russia argues that the expansion of Nato into eastern Europe and its courting of Ukraine has been a repeated provocation.

A Nato official said: “Deterrence, based on an appropriate mix of nuclear, conventional and missile defence capabilities is a core element of our overall strategy. We cannot go into detail on our nuclear discussions. These are internal, sensitive and classified matters. What I can say is that Nato continuously assess all aspects of Russia’s military activities, including Russia’s nuclear rhetoric.”

A second Nato official said: “The Russian leadership is rhetorically lowering the threshold when it comes to nuclear weapons and this is something which should not be done. It largely wasn’t done even during the cold war.

“This kind of nuclear threat was something which we found quite surprising, quite negative and is something we believe should be avoided but we are closely examining it carefully as part of the overall examination of Russia’s activities in Europe and how we at least in Nato must unfortunately react.”

Fallon announced on Wednesday evening that the UK is to double its spending on training Ukrainian troops from £3m to £6m.