Stakes raised in Ukraine crisis
Ukrainian government troops have destroyed a number of separatist checkpoints in the east
The crisis in Ukraine is entering a new and more dangerous phase where all of the parties involved have to determine what level of risk they are prepared to take to try to ensure their recipe for the country's future prevails.
The Ukrainian government in Kiev - after a shaky start - has finally begun to try to seize back control of eastern towns and government buildings from pro-Russian gunmen.
Instead of melting away or handing their armoured vehicles over to the "green men", pro-Kiev security forces are fighting and fighting hard.
The rebels have shot down several Ukrainian military helicopters
They are taking casualties, but they are inflicting greater casualties on their opponents. Their helicopter losses to shoulder-fired surface-to-air missiles are significant - another sign, say Nato insiders, of the professional help being afforded to the separatists by Russia.
On the political front the government in Kiev insists that any locally-organised referendums or ballots in the eastern part of the country will be illegal. It looks forward, as planned, to holding a nationwide presidential ballot on 25 May.
'Calling Moscow's bluff'Russia's goals in this crisis have not changed. Moscow insists that it is simply acting to protect fellow Russian-speakers.
But Western leaders believe that it is intent upon wrecking any chance of holding truly national presidential elections. Its longer-term aim is to undermine and weaken the government in Kiev.
However, on the ground the balance of advantage may be subtly changing.
President Putin may have some tough decisions to take in the near future
While many buildings and roadblocks remain in separatist hands, the Kiev government's ability to mount a reasonably effective security operation has raised the stakes for Moscow.
Russia hoped that by massing troops on Ukraine's frontier - while seeking to infiltrate and undermine Kiev's authority from within - it could achieve a looser, more decentralised Ukraine.
For a while this seemed to be working. Kiev's authority was cowed and the willingness of its troops to fight was questionable.
That seems to have changed. Kiev is in effect calling Moscow's military bluff, bringing closer the moment when President Vladimir Putin must decide whether or not to use overt military force.
The separatist-backed referendum in the Donetsk region is planned for 11 May
That is why this current moment is so dangerous.
Kiev is trying to calibrate its security operations in such a way as to avoid forcing Russia's hand. This will take a good measure of skill as well as luck.
Clumsy operations that lead to significant civilian casualties could change the Kremlin's calculations.
Indeed, the danger of an unplanned incident on the ground changing the terms of this conflict is real and ever present. The fire in Odessa that cost more than 40 lives is a good example of this kind of escalation.
'Adversary'Meanwhile, the outside world looks on with mounting concern at a political landscape that at a local level is beginning to look like a scene from the conflicts in Bosnia or Kosovo.
The West is united in its backing for the Kiev government and the condemnation of Russia's role inside Ukraine is ever more strident.
Nato Secretary General Anders Fogh Rasmussen has gone so far as to describe Russia as more of an adversary today than a partner.
But still the West's rhetoric is much tougher than its actions. There clearly is a hope that the token sanctions so far will have caught Mr Putin's attention.
That may be an illusion.
What is really concentrating his mind is Kiev's willingness and ability to fight back. The Ukrainian security operations have only made modest progress. Difficult days lie ahead.
But Russia now has to weigh up if it has achieved as much as it can by covert means.
And it must make an assessment of the likely consequences of giving its troops a green light to advance.
The West's response so far has been limited. But can Mr Putin really bank on the likelihood that this state of affairs will continue?
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