"The old security formats developed right after the World War II are not working. I raised the issue of peacekeepers," he said.
"The aggressor did not need the Crimea. The aggressor has one-sixth of the land on the planet ... Today we have reasons to believe that the aggressor needs the whole of Ukraine," Poroshenko said, according to Ukrainian News.
He added that Russia wants to see Ukraine weak.
He noted that he would do everything possible to preserve the unity of the country.
"I will do everything possible to ensure that no language, no faith, no question of land, no other questions would split Ukraine," Poroshenko said.