Ukrainian President Petro Poroshenko has apologized for mistakenly forecasting a rapid completion of the anti-terrorist operation (ATO) in eastern Ukraine in 2014.

"I said over four years ago that the ATO would take hours instead of months. The context of my statement is irrelevant. [...] I am sorry for giving excessive expectations. I sincerely apologize for giving hope that did not come true. It is a pity that I did not keep my promise. My apology," Poroshenko said at the Ukrainian flag's hoisting ceremony in the city of Dnipro (former Dnipropetrovsk) on Thursday.

The president said for him it was a serious lesson of careful and responsible attitude to his words and promises.

"I made conclusions from it. From the very beginning it was necessary to direct everyone for a long and exhausting struggle. Many of us in the spring of 2014 did not realize the real depth of the catastrophe that occurred before the war. The army was disarmed and stripped, sold and robbed beforehand. Many of us saw the situation as a rebellion of separatists. Yes, artificial. Yes, it was organized from Moscow. Yes, it was financed and armed by the Russian military, but still a rebellion," Poroshenko said.

He said that only then it became clear that this was "another full-scale Russian-Ukrainian war."

According to the president, Ukraine quickly gathered all the available resources and liberated in several weeks a greater part of Donbas, dozens of cities, villages, towns, millions of people and really brought the ATO to its victorious final. He recalled that Russia in late August 2014 "invaded Ukraine by its regular units," which radically changed the military-strategic situation and all calculations on the resources, time and intensity of the operation.

"There was and only one way - to build a large and strong army capable of keeping the defense against the much more numerous armed forces of Russia," Poroshenko said.

He said that only a modern, combat-ready army can ensure peace on Ukrainian soil.

"We do not want anything more than peace, and no one wants peace as much as we do. Peace will surely come to our land. Only an efficient army can provide it, and it gets stronger day by day [...] Missiles, cannons, tanks and planes are important to our army. But our Flag, which unites us and leads to victory, also remains necessary," the president said.