True to all past form the fighting in eastern Ukraine continued throughout yesterday threatening to derail the peace deal created earlier last week by the leaders of France, Germany, Russia and Ukraine.

A truce should come into force today but it only seems to have spurred on the Russian-backed separatists to hold on to their gains around the vital hub of Debaltseve, north-east of Donetsk and scene of some of the fiercest fighting against Ukrainian forces. The threat of all-out war between east and west may have been lifted but those involved in last week's talks insist that the danger has not gone away. Even German diplomats close to the indefatigable Chancellor Angela Merkel admit that the present deal is "better than no deal".

Before yesterday's maelstrom it all looked so positive. As the leaders paused to regain their breath President Francois Hollande spoke of the "relief to Europe" that would follow if the truce actually comes into being and if the rival Ukrainian and rebel forces withdraw their heavy weapons from the eastern half of the country. Another danger has also abated: only a week ago it seemed inevitable that Washington would make good its threat to send weapons to the government of President Petro Poroshenko the recently elected pro-European leader of Ukraine.

Although that possibility has been sidestepped it is hard to avoid the impression that disaster has only been averted for the time being. On one level any ceasefire has to be welcomed, not least by the beleaguered people of eastern Ukraine who have been under ceaseless shellfire for the past five months, but is difficult to imagine that it will be permanent. The new border between Ukraine and Russia looks awfully porous as do the 50km buffer zones around the main centres of population and their security will depend on Russian willingness to police their own fighters in unmarked uniforms who have been supporting the separatist forces.

Because no provision has been made for the insertion of an independent peace-keeping force, President Vladimir Putin is still free to continue meddling in the affairs of Ukraine for as long as it suits Russia's interests. Throughout the crisis which began with the annexation of Crimea in the spring of 2014 Putin has worked hard to destabilise Ukraine not just because he wants to have a foothold in the country but because he wants to thwart Poroshenko's ambitions to join the EU and Nato. As long as that issue remains unaddressed there is little likelihood that he will reduce Russian pressure in the region. After all, Putin regards western encroachment in Ukraine both as a strategic liability and as an existential threat to the concept of Russian territorial integrity.

All that can keep him in check is the possibility of further EU economic sanctions but he will also have noted that last week's Minsk agreement included an EU-backed loan of $17.5bn from the International Monetary Fund which has been described as "a diplomatic sweetener" aimed at helping Poroshenko to get Ukraine back on an even keel ahead of his application to join the EU. Before any improvements take place, it could be in Putin's interests to hamper those reforms by keeping open the border with Ukraine and maintaining his surreptitious support of the separatist forces. Already it seems inevitable that eastern Ukraine will become a de facto Russian cantonment which will control the transport links into Russia and could even threaten the industrial port of Mariupol on the Sea of Azov. Much will depend on the outcome of the local council elections promised for later this year.

Seen from that perspective the Minsk agreement looks hugely beneficial to Putin and the precise opposite to Poroshenko who could only put a brave face on the outcome. It could also explain the Russian leader's last-minute obfuscation on the position of the forces besieging Debaltseve. Everything in Putin's tactics points to a continuation of the interference in the affairs of Ukraine which led to the current instability. Just as importantly from his point of view he has managed to quash the threat of US supplying arms to the Ukrainians. The fragility of the Minsk truce and yesterday's fighting show that nothing has been resolved and a great deal remains to be done before there is any lasting peace.