KIEV — President Petro Poroshenko said on Wednesday that Ukraine was prepared to introduce martial law nationwide if the separatist conflict in the east escalates further, news agency Interfax reported.

Speaking ahead of a peace summit of leaders of France, Germany, Russia and Ukraine, Poroshenko said Kiev's key position at talks would be aimed at securing an unconditional ceasefire, but Ukraine was prepared to defend itself militarily if needed.

"I, the government and the parliament are ready to take the decision to introduce martial law in all the territories of Ukraine," he was quoted as saying at a government meeting.

"We are for peace ... (but) our country needs to be defended and we will do that to the end," he said.

Ukraine's Russian-backed separatists have launched some of the war's worst fighting in an assault on a government garrison, dimming hopes of a lasting ceasefire agreement at Wednesday's talks in Minsk, Belarus.

The rebels have said they want independence and have set up 'people's republics', but Poroshenko said Ukraine would remain a unified state.

"Ukraine has always been and always will be a unified state ... federalization is a seed that will not take root in Ukrainian soil," he said, referring to proposals pushed by Moscow.