If the peace initiative fails, the Ukrainian president promises to amend changes to a legislation, which would allow mobilization, the country's news agency UNIAN reports.
"Even before Minsk, during a meeting of cabinet ministers I warned that we would need to take harsh but neccesary decisions on introduction of the martial law if there was no peace. In this case martial law would be introduced not only in Donetsk and Luhansk, but all over the country," he said.
The ceasefire between Kiev forces and independence supporters in eastern Ukraine is due to come into force at midnight local time on February 15 (February 14, 22:00 GMT).
The ceasefire was one out of the measures agreed on during the last reconciliation talks on Ukraine in the Belarus capital of Minsk Thursday.
After the 'Normandy four' talks end, Ukrainian President Poroshenko flatly rejected the idea of granting a broad autonomy to the eastern Donbas region, and of making Ukraine a federation that was part of the agreements reached in Minsk that day.
The leaders of Ukraine, France, Germany, and Russia held a 16-hour summit in Minsk on Wednesday and early Thursday. The talks resulted in a new political deal aimed at stopping the deadly conflict in eastern Ukraine.
The deal was signed by the Contact Group on Ukraine, including envoys from Moscow, Kiev, the self-proclaimed people's republics of Donetsk and Luhansk and the Organization for Security and Co-operation in Europe (OSCE).