MUNICH (Reuters) - Britain's defence minister voiced concern on Friday that Russia may have "lowered the threshold" for using nuclear weapons and said Britain must update its own deterrent in response to Russian modernisation of its nuclear forces.
Russia's nuclear strategy in a hypothetical future war is coming under greater scrutiny among NATO members as tensions between the Western alliance and Moscow hit their highest level since the Cold War over the Ukraine conflict.
"There is three-fold concern, first that they (the Russians) may have lowered the threshold for use of nuclear. Secondly, they seem to be integrating nuclear with conventional forces in a rather threatening way and ... at a time of fiscal pressure they are keeping up their expenditure on modernising their nuclear forces," Defence Secretary Michael Fallon told Reuters in an interview.
"All of that is very worrying," he said during the Munich Security Conference. "The main answer to that is to make sure that we modernise our own deterrent too."
Russia's new military doctrine reserves the right to use nuclear weapons in response to a nuclear strike or a conventional attack that endangered the state's existence, but some in the military had been calling for a first strike option.
Fallon did not expand on how Russia could be lowering its nuclear threshold.
Britain is set to take a final decision next year, after this year's election, on whether to replace its ageing fleet of Vanguard class submarines, which carry Trident nuclear missiles.
Fallon's Conservative party, the senior member of the two-party ruling coalition, favours a like-for-like replacement of the submarine fleet.
Fallon also voiced concern about stepped-up patrolling near Britain's coast by Russian bombers, ships and submarines.
"We've seen a sharp increase in Russian activity, not simply just at the edges of UK airspace, but affecting a number of other allies in NATO," he said.
An incident last week when two heavily-armed Russian bombers flew into the English Channel was "something we've not seen for as long as anybody can remember", Fallon said.
The Russian flights were provocative, intimidatory and "frankly they are dangerous because there are pilots who are not responding to air traffic control, not filing flight plans and not responding to our own pilots", he said.
Fallon spoke out against supplying weapons to Ukraine, an option which is under consideration in Washington.
Asked if Britain would follow suit if Washington decided to send weapons, Fallon said: "No, we are not supplying lethal equipment to Ukraine. We think that would escalate the conflict. We have been supplying non-lethal equipment and training already and we continue to keep that under review."
He said Britain backed a new effort by the leaders of Germany and France to try to halt the Ukraine conflict, but said the West also needed to keep up sanctions pressure on Moscow.
Territorial gains made by Ukrainian separatists since the Minsk agreement in September should "absolutely not" be recognised in any new ceasefire, he said.
(Story refiles to add minister's full name in third paragraph)
Reporting by Adrian Croft; Editing by Toby Chopra