"On Friday in Minsk a document will be signed providing for the gradual introduction of the Ukrainian peace plan," he said on the sidelines of the NATO summit in Wales.
"It is very important that the first element provides for a ceasefire," he said.
Representatives of Kiev, Moscow, the separatist rebels and the pan-European security group the OSCE are due to meet in the Belarussian capital on Friday.
"If the meeting takes place, I will issue instructions to the leadership of the general staff about a bilateral ceasefire," Poroshenko told Ukrainian television.
He also said that NATO will adopt a declaration backing stronger military support for Kiev, a move that is likely to infuriate Moscow.
"In its declaration, NATO will confirm resolute bilateral steps by its member states to support military and technological assistance for Ukraine," Poroshenko said. "This is exactly what we were waiting for."
Russian President Vladimir Putin had announced yesterday a seven-point ceasefire plan for Ukraine, although he denies Moscow has any involvement in the conflict raging in the east.     

But Moscow is vehemently opposed to closer ties between NATO and Kiev, which has said it is taking steps to begin the membership process for the transatlantic alliance.

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