The Kremlin insists that the next Normandy-format summit should conclude with "cast iron agreements" committed to writing.

"There are three important preconditions that we think, if implemented, could ensure success of this summit, " Russian presidential aide Yury Ushakov said at a briefing on Friday.

"Thus, it is necessary to finally settle the issue of disengagement in the three so-called pilot areas, Stanytsia Luhanska, Zolote, and Petrivske, on the contact line," Ushakov said.

"This issue has been discussed by aides to the [Normandy Four] leaders and by the [Trilateral] Contact Group for quite a long time," he said.

"We also consider it important, ahead of the summit, that the TCG put in writing the so-called Steinmeier formula whereby the law on a special status for Donbas is enacted temporarily on election day and permanently following the election and a final OSCE/ODIHR report," Ushakov said.

"We know that at earlier meetings, the summits in Paris and Berlin, certain agreements were reached which were not always honored by Ukraine," he said.

"We want there to be a cast iron agreement which would enable further real steps toward a settlement of the crisis," Ushakov said.

"It is necessary, apart from TCG agreements, to draft a text for the leaders to adopt toward the end of the summit," he said.

"This is very important. The substance of this summit should be recorded on paper," Ushakov said.