According to Petro Poroshenko, 50, Putin, the world's most powerful man according to Forbes wants "the whole Ukraine" to be part of the "Russian Empire."
Russia recently conducted military drills in Crimea, the peninsula it annexed from Ukraine in 2014 -- but this military move is regarded by a lot of Nations as illegal and unwarranted.
"It is absolutely the same situation like Russian bombardment in Aleppo," he told CNN's Christiane Amanpour in an exclusive interview on Wednesday night.
"They have only one purpose -- [the] world should be less stable, less secured."
Had you asked him in 2013, Poroshenko said, if it would have been possible for Russia to "occupy the Crimea," he would have said "no, this is not possible -- there is some red line, and Putin [will] not cross this line."
"If you asked me in January, year 2014," he went on, if it was possible that "thousands of Russian regular troops will penetrate on Ukrainian territory in the east of my country in July and August," I would have said, "no, this is not possible."
With those moves, he said, the world "is completely changed."
"Russian aggression completely destroyed the post-war global security system,"