Jens Stoltenberg says Nato will never withdraw its conditional offer of membership to Ukraine

The risk of conflict is real as Russia continues to mass its forces and artillery on the borders of Ukraine and make demands that it knows are unacceptable, Jens Stoltenberg, the Nato secretary general, has warned.

Earlier, Nato foreign ministers held a final symbolic display of transatlantic unity before a set of three separate critical talks next week with Russia on Moscow’s demands to restore past spheres of influence and have Nato strategic weapons withdrawn from near Russia’s borders.

Russian leader’s speech to top commanders comes as tensions grow with the west over Ukraine

Vladimir Putin has said he will consider a military response if Russia feels threatened by Nato, in a sign that he is not ready to de-escalate tensions over a potential invasion of Ukraine.

In a combative speech on Tuesday, Putin – who has demanded “security guarantees” from Nato – told his top military commanders that the west was to blame for the rising tensions. It came against a backdrop of a Russian buildup of tanks and artillery for what could constitute an invasion force within weeks.

Contentious security guarantees Moscow is seeking include a ban on Ukraine from entering Nato

Russia has put forward a highly contentious list of security guarantees it says it wants the west to agree to in order to lower tensions in Europe and defuse the crisis over Ukraine, including many elements that have already been ruled out.

The demands include a ban on Ukraine entering Nato and a limit to the deployment of troops and weapons to Nato’s eastern flank, in effect returning Nato forces to where they were stationed in 1997, before an eastward expansion.