Deputy chief of Ukraine's Main Military Intelligence Directorate (GUR) Vadym Skibitskyi made the assessment on Wednesday.
He said Russia had 462,000 army personnel in Ukraine, "the entire land component of the Russian military," as cited by the Institute for the Study of War, a US think tank.
According to Skibitskyi, this currently allows Russian commanders to rotate units "throughout the theater" of the war.
Those at "50% or less of their intended end strength" are withdrawn from the front, and later returned after "recovery and replenishment," the Ukrainian official said.
While such rotations will likely enable Russia to maintain the pace of localised offensives in eastern Ukraine in the near term, it is unclear if Russia will be able to rotate units "in the long term or in the event of intensified Russian offensive efforts or a significant Ukrainian counteroffensive operation," the ISW assessed.
Friday is day 688 of Russia’s war on Ukraine.
Russia invaded Ukraine on February 24, 2022, launching the largest military campaign in Europe since World War II.
Source: ISW, Kyiv Post, The Kyiv Independent