He said in a commentary to Reuters, Censor.NET reports.
Poroshenko also said that Ukraine expected to get clearance for visa-free travel to the European Union for its citizens within a "very few" weeks after meeting the bloc's requirements.
An agreement reached last month after weeks of stalling has yet to come into effect.
"This is a direct obligation of the EU....We are waiting for the very few moments or weeks for finishing the paperwork for these things and launching," he said.
Poroshenko is also confident of getting Crimea back from Russia, which denies sending troops or military equipment into Ukraine. Kiev this month filed a lawsuit at the United Nations' highest court demanding that Russia halt support for pro-Moscow separatists fighting in eastern Ukraine..
Asked whether Ukraine would ever regain Crimea, Poroshenko said: "I have no doubt. This is Ukrainian territory, Ukrainian people. This was brutal violation of international law."
On Dec. 7, 2017, President Petro Poroshenko said EU leaders had reached a compromise on visa suspension mechanism. This removed the last hurdle on the way to visa liberalization for Ukrainians.