Andriy Yermak also told Sky News that he hoped Ukraine would “soon” defeat the Russian invading forces and secure victory. Mr Yermak paid tribute to Scott Sibley, 36, the first British national to be killed fighting for Ukraine against Russian troops. “We remember – this hero will be in our hearts,” he said. The bombings in Mariupol continue after the evacuation – live updates The head of the office of President Volodymyr Zelenskyy described the pressure of more than two months of war, saying that the discovery of mass graves and evidence of war crimes in the city of Bucha and elsewhere outside Kyiv was one of the darkest moments. Mr Yermak said that if Russian forces tried again to move against the capital they would lose, having already been thwarted in an initial attempt during the first phase of the invasion. Use the Chrome browser for a more accessible video player 3:01 Russian advance “has stopped in the east” “We will fight to the end, until our whole territory is under the control of the Ukrainian government,” he said in an interview in English, sitting at a table in a meeting room deep inside the heavily fortified President. Office in Kyiv. Russian Vladimir Putin has spoken out strongly about his nuclear arsenal during the crisis, sparking concerns that he could use nuclear weapons against Ukraine. However, Mr Yermak said a Russian tactic was to use blackmail to intimidate an opponent, either by threatening to cut off energy to Europe or by threatening to use chemical or nuclear weapons in Ukraine. Image: Police working on the identification process after the killing of civilians in Bouha. Photo: AP He noted that, as President Zelensky said, the nuclear threat from Russia does exist. But Mr Yermak said: “I personally do not believe that Russia will use nuclear weapons.” He said: “People who make these decisions want to live – and if they start using nuclear weapons it will be the end, not just for a soldier. It will be a new nuclear war and no one knows who will be alive after that. “ Read more from Sky News: What nuclear weapons does Russia have? Russia is “concerned” about its nuclear capability Asked if it would actually mean the end of the world, he said: “Yes, these people really want to be alive to take so many risks.” As for the war effort, which now focuses on eastern and southeastern Ukraine, the top aide stressed the vital importance of Western weapons in helping Ukrainian forces fight. “It is one of the conditions for our quick victory and victory without many losses,” he said. “Now we pay the highest price, because we pay with the lives of our people.” Follow the Daily Podcast on Apple Podcasts, Google Podcasts, Spotify, Spreaker Mr Yermak spoke warmly of the strong friendship and support from the United Kingdom, describing British Prime Minister Boris Johnson’s visit to Kyiv in April to see Zelensky as “a great inspiration”. He said the two leaders’ decision to leave the Presidential Palace complex and take a walk in the capital to Independence Square was spontaneous – to the surprise of their security guards. “It was a big shock for security but so happy for the people.” As for how long he thought the war in Ukraine would last, Mr Yermak said: “I hope not too much. Maybe some want it to be too long. I think most Ukrainians want it to end as soon as possible. But we will be on top. of our victory ίζω I hope that we will win soon and I am sure of that “.