New Delhi, Feb. 7 -- Ukrainian President Volodymyr Zelenskyy on Friday described the performance of the air force in parts of the country as "unsatisfactory," and said that steps are being taken to improve the response to large-scale Russian drone barrages of civilian areas.

The repeated Russian aerial assaults have in recent months focused on Ukraine's power grid, causing blackouts and disrupting the heating and water supply for families during a bitterly cold winter.

With the war about to enter its fifth year later this month following Russia's all-out invasion of its neighbor, there is no sign of a breakthrough in U.S.-led peace efforts following the latest talks this week. Further U.S.-brokered meetings between Russian and Ukrainian...