Top diplomats from the four countries, whose leaders hammered out the initial peace plan in the Belarussian capital Minsk, were to meet in Paris, with Kiev accusing Moscow and pro-Russian rebels on the ground of torpedoing the truce.
"The Minsk agreements are not being respected and everyone has to say clearly that this can not go on," a high-ranking Ukrainian diplomatic source told reporters here.
Fighting has dropped off significantly since rebels ignored a truce to seize the strategic transport hub of Debaltseve last week, but clashes still continue around
strategic flashpoints.
Ukraine's military said its forces in the conflict zone came under fire 12 times overnight and rebels had again tried to storm a village east of key port town Mariupol.
The continuing clashes have delayed a pull-back of heavy weapons that was due to start a week ago under the peace plan. Kiev refuses to withdraw its big guns from the frontline until the shooting stops definitively.
The rebels have claimed several times that they have started to withdraw arms but this has not been confirmed by monitors from the Organisation for Security and Cooperation in Europe (OSCE).
The latest fighting came as Putin -- whom Kiev and the West accused of masterminding the conflict -- said he thought the prospect of all-out war between Russia and Ukraine was unlikely.
Asked in an interview with Russian state television if he thought the current situation could lead to a direct confrontation, Putin said: "I think that such an apocalyptic scenario is unlikely and I hope that it will never happen."
"If the Minsk accords are complied with, then I am sure that the situation will gradually get back to normal."
He added: "No one needs a conflict, moreover an armed one, on the periphery of Europe."
Ukraine has accused Russia of sending in more tanks to bolster rebel forces around Mariupol, the latest allegation that Moscow is spearheading the insurgency.
Moscow denies it is sending arms and troops to bolster the rebels. However it made similar denials over Crimea – the Ukrainian Black Sea peninsula that it annexed last year – before finally admitting that it had deployed troops.
If Mariupol were to fall to the pro-Russian rebels, it would remove a key obstacle to creating a separatist land corridor stretching from Russia's border with Ukraine to Crimea.

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