Petro PoroshenkoRussia's UN ambassador Vitaly Churkin has denounced Ukraine's call for the deployment of UN peacekeepers in eastern Ukraine as a destructive move.
The Ukrainian president's call "raises suspicions that he wants to destroy the Minsk accords", Mr Churkin said.
The Minsk ceasefire deal was reached a week ago but fighting round the strategic city of Debaltseve saw the withdrawal of Ukrainian troops there.
Russian-backed rebels in eastern Ukraine also criticised the proposal.
Mr Churkin accused Ukrainian President Petro Poroshenko of seeking a new scheme instead of doing what he had signed up to.
"If one proposes new schemes right away, the question arises whether [the accords] will be respected", he said.
The leadership of the self-proclaimed Donetsk People's Republic described the call for peacekeepers as a violation of the Minsk accords and asked the other parties to the deal - Moscow, Berlin and Paris - to influence Kiev.
The leaders of all four countries will discuss the situation over the phone again on Thursday, a statement from the Kremlin says.
Mr Poroshenko called for UN-mandated peacekeepers to enforce the ceasefire after fighting continued following the rebel advance on Debaltseve.
A police mission by the European Union would be the best format for a peacekeeping operation, Mr Poroshenko said on his website.
It would help guarantee security "in a situation where the promise of peace is not being kept", he told an emergency meeting of Ukraine's national security and defence council.
Nearly 2,500 Ukrainian soldiers withdrew from Debaltseve on Wednesday.
Mr Poroshenko said the withdrawal had been organised, but that at least six soldiers were killed and more than 100 wounded.
Earlier, a senior Ukrainian military official said 22 Ukrainian soldiers had died in Debaltseve over the past three days. Rebel claims of a much higher figure have been dismissed by the government.
The ceasefire, which officially came into effect on Sunday, has been broadly observed elsewhere in eastern Ukraine and some heavy weaponry is said to have been withdrawn by both sides.
However, monitors from the OSCE security group have been unable to reach Debaltseve.