Mykhallo Podolyak, a Ukrainian negotiator and presidential advisor, said on Sunday that: "Russia is already beginning to talk constructively ... I think we will achieve some results literally in a matter of days".

That was echoed by the Russian delegate, Leonid Slutsky, who said: "According to my personal expectations this progress may grow in coming days into a joint position of both delegations, into documents for signing".

And, late on Tuesday Australian time, Ukrainian President Volodymyr Zelensky said negotiations were "going quite well": "Over this [the question of the end of the war] our delegation also worked at the talks with the Russian side. Pretty good, as I was informed. But we'll see. Will be extended tomorrow."

While these developments have been overshadowed by horrific imagery out of the besieged city of Mariupol where at least 2500 civilians are reported to have been killed, they suggest both sides have had a harsh reality check and realise this cannot go on.

Putin has faced much stiffer resistance on the ground and a swifter and more Draconian response from the West than he could ever have expected. His generals have made mistakes, his supply lines appear to be overextended and a flood of Western military aid is giving the Ukrainians the means to fight back like tigers.

Ukrainians, meanwhile, have been transported back in time to some of the bloodiest days of World War II when civilians were deliberately targeted, fighting was from house to house and cities containing millions of people were encircled and besieged.

While President Zelensky has emerged as a heroic figure is he really prepared to allow Kyiv, a city of almost three million people, to suffer such a fate? Are the Ukrainians prepared to destroy the village in order to save it?

Mariupol, now a city of mass graves and bodies in the streets where schools and hospitals have been levelled and hundreds of thousands of people are without food, water, electricity or heat, is being subjected to a tactic as old as warfare itself. That is that the stronger the resistance a city under siege puts up the greater the devastation that is wrought upon it.

The psychology behind this brutality is that if an example is made of one stronghold then others are more likely to surrender without putting up a fight.

This is an indication of the level of medieval barbarity to which the Russian forces are prepared to sink in what has now become a brutal war of attrition.

While it is probable war crimes have been committed by now, the Ukrainians are fighting for their survival while their opponents - albeit many of whom are conscripts - are trained combatants. President Putin sacrificed any claims he had to legitimacy when he sent his troops across the border.

That said, it is difficult to see how peace can be negotiated unless Zelensky grants concessions to Russia. If this situation is to be defused Putin needs a face-saving exit strategy. Unless he gets it the conflict will escalate, possibly dragging in NATO partners, and the world could be staring into the nuclear abyss.

President Zelensky has already said Ukraine is willing to "discuss and find a compromise on how these territories [Crimea, Donetsk and Lugansk] will live on" but that "we're not ready for capitulation".

The question of Ukraine's possible future membership of NATO also needs to be resolved.

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