Russia is pushing for a new "treaty on European security" to govern East-West relations, arguing that Nato is a Cold War relic.
Nato officials say such a treaty would weaken the alliance and reward Russian "aggression". William Horsley, a writer on European affairs, examines what is at stake.
Russia has tightened its grip on South Ossetia since the August war
Top Nato officials and diplomats met this month at the Wilton Park conference centre near England's south coast to discuss how to resolve doubts and divisions about the alliance's future before its 60th anniversary summit in April.
Nato's problems in Afghanistan topped the formal agenda. But the loudest alarm was sounded about the danger of a long-term confrontation with Russia.
Some journalists were invited in on condition that speakers would not be named without their consent. The depth of their concern is clear from statements like these:
"Russia's action in Georgia was no aberration. It may have become the norm."
"Russia must not have a veto on which countries can join Nato. If we concede that we're finished."
"Russia is aggressively trying to establish its sphere of influence and to rewrite the rules based on Russian national interest, not on international rules."
Nato strategists are worried at the growing list of what they see as belligerent Russian actions:
- Its seizure of territory in Georgia and unilateral recognition of breakaway South Ossetia and Abkhazia
- Its latest use of natural gas as a political tool this month, aimed at least partly at discrediting Ukraine as a would-be Nato member
- What US officials say is Russia's abandonment of democracy
Moscow is showing flexibility over its Baltic missile deployment
There was wide agreement that Europe, too, has made mistakes. "Europe has stupendously failed with Russia," said one participant.
Nato's biggest headache is the lack of a common accord about what to do about it.
While the divided West laments the dark turn of events, the Russians have put forward their own plan for a new, overarching security treaty for Europe.
Russia set out the broad lines of the proposal last month to the Organisation for Security and Co-operation in Europe (OSCE), where Russia is a member along with the US and 54 other states.
The Russians claimed that such a new treaty would allay mutual suspicions and fears, improve the current, failed arrangements for conflict resolution in Europe, and give new guarantees for the equal security of all states.
Worries about freedom
But the proposal also contained what could be seen as a veiled threat. Russia wants a new agreement on "comprehensible" rules of the game, "to avoid having to rely exclusively on national means... to ensure security".
Russian commentaries have made clear that one aim is to water down the commitments of OSCE states to international human rights standards, including election monitoring and media freedom.
The Russian proposal lists the building-blocks of such a treaty, including "respect for the sovereignty, territorial integrity and political independence of states".
A western diplomat at the Wilton Park meeting responded acidly that Russia had trampled on the rules of international conduct by its military action in Georgia, and was now demanding the West's acceptance of that violation as a condition of further dialogue.
"It's reminiscent of old Soviet tactics and we won't fall for it," the diplomat said.
But Russia may have some powerful levers with which to widen Nato's internal splits, and seek to rewrite the rules of East-West relations.
Nato is preoccupied with building security in Afghanistan
Some European leaders have voiced sympathy with Russia's call for a new security set-up - notably France's President Nicolas Sarkozy. At an EU-Russia summit in Nice last November he backed President Medvedev's idea for an international summit this year to discuss Russia's ideas.
Mr Sarkozy gave further encouragement to the Russians by saying that the US missile defence system would not help Europe's security, and might harm it.
Later he backed down and France along with other Nato foreign ministers formally closed ranks in support of the missile defence plan.
But many European capitals have taken note of Russia's message - that Russia will be no threat to them if only Nato changes course, on missile defence and on its collective pledge of eventual membership for Georgia and Ukraine.
And Alyson Bailes, former head of the Stockholm International Peace Research Institute, is among those Western security analysts who say that a new comprehensive code, taking account of Russia's own keenly-felt fears, is "not a stupid idea".
It could provide a framework, she says, for new arms control pacts with Russia of the kind that US President Barack Obama has promised to seek. And Europe cannot expect settled relations with Russia by ignoring its perception that it is threatened by Nato's expansion along its western borders.
So does Russia want stability, or to exert its power by the threat or use of force? It has sent out confusing signals.
This week Russian military officials seemed to put out an olive branch, linking a suspension of their plans to deploy short-range missiles in Kaliningrad - the Russian enclave between the two Nato states of Poland and Lithuania - with the suggestion that President Obama should at least pause America's plans to deploy a missile defence system in Poland and the Czech Republic.
Yet Russia has also let it be known that it wants to build a naval base for its warships on the Black Sea in Georgia's breakaway region of Abkhazia, which would break last year's ceasefire accord again.
Nato member states all want to resume a constructive dialogue - but they differ about how far to bend to Russia's will
And Russia is still refusing to let OSCE military monitors return to South Ossetia to restore an international security presence there, six months after the fighting.
Behind the scenes the Russians' tactics have provoked high diplomatic tensions. An official present at December's OSCE ministerial meeting in Helsinki, where Russian Foreign Minister Sergei Lavrov unveiled the treaty plan, said he witnessed angry exchanges of a kind rarely seen since the Cold War.
Nato's Secretary General Jaap de Hoop Scheffer has bluntly warned against entering talks with Russia on anything that could undermine the alliance as the guarantor of Western security.
But the OSCE is a separate body, designed for a range of "soft" security issues, such as border control and safe management of nuclear materials, as well as setting a framework for military and political co-operation. Greece, currently chairing the OSCE, plans to arrange a high-level meeting later this year as the Russians wish.
The issue could be politically explosive for Nato. A national security adviser to Polish President Lech Kaczynski, Witold Waszczykowski, said at Wilton Park that Russia's security treaty idea was aimed at "the dissolution of Nato". Poland, he added, would block any high-level meeting to discuss it.
The governments of Poland and the Czech Republic say their carefully-laid plans to host missile defence bases are vital to their long-term security under America's protection. They have warned sharply against moves to undo those plans in dealings with Russia over their heads.
But Russia seems to have been emboldened by the European Union's failure down the years to speak out loudly or with a single voice against its provocative behaviour - its efforts to control Europe's gas supplies from the east, or to foment nationalism among ethnic Russians living in the Baltic states, or Prime Minister Vladimir Putin's threats to target Western cities with nuclear weapons in response to the missile defence shield.
Here is the dilemma for the West: Russia has limited contacts through existing channels, including the Nato-Russia Council, since the August war in Georgia. Nato member states all want to resume a constructive dialogue. But they differ about how far to bend to Russia's will.
This combustible mix of disputes suggests that Russia's relations with the West may be approaching some kind of turning-point. A lot is at stake for all sides.
They will all be represented at the annual Munich Security Conference which starts on 6 February. High on the agenda there is the future framework for European security.
William Horsley is media freedom representative for the Association of European Journalists.