Kiev, Dec 20 : Ukrainian President Volodymyr Zelensky said at his annual press conference that "no one knows" when will Russia's continued war against his country will end. "I think that no one knows the answer. Even respected people, our commanders and our Western partners, who say that the war will last many years, they do not know," Zelensky said at the press conference on Tuesday night. Commenting on Ukraine's achievements in the war this year, Zelensky said that Ukraine gained a "major victory" in the Black Sea, reports Xinhua news agency. "In Ukraine and abroad, everyone can appreciate that the Russian fleet was deprived of their total dominance in the Ukrainian Black Sea," Zelensky said, insisting that Russia "hasn't achieved any of its goals" this year. While speaking on Ukraine's counter-offensive, Zelensky said the fact that Kiev didn't control the sky and didn't have enough ammunition had impacted the military operations in the southern regions this year. The President said that military commanders have offered him to mobilize an additional 450,000-500,000 soldiers to participate in Ukraine's defense and potential counteroffensive operations, but the decision on their mobilization has not been approved yet. Asked about the prospects of joining parts of Ukraine to the NATO, Zelensky said the option is out of the table due to certain risks. He also noted that Kiev has not received any official proposals regarding the "partial accession" to the alliance. Commenting on strengthening Ukraine's defense capabilities, the Ukrainian leader said that soon his country will receive several new Patriot air defense systems and National Advanced Surface-to-Air Missile Systems from its partners. Besides, next year, Ukraine plans to produce about 1 million drones, Zelensky added. /IANS