Volodymyr Zelenskiy said on Monday that the situation at the front in the Donbas region was "difficult and painful" and required all of the country's "strength and concentration".
Ukraine’s president warned on Boxing Day that power shortages still persist, with nearly 9 million going without electricity.
"First of all, matters at the front. Bakhmut, Kreminna and other areas in Donbas, which require a maximum of strength and concentration." Zelenskiy said in his nightly video address.
"The situation there is difficult and painful. The occupiers are deploying all resources available to them -- and these are considerable resources - to make some sort of advance."
Mr Zelenskiy said in his nightly video address that power workers repairing the grid after repeated Russian attacks had reconnected many people over Christmas but problems remained.
"Naturally, shortages persist. Blackouts are continuing," he said.
"The situation as of this evening in different regions of Ukraine is that nearly nine million people are without electricity. But the numbers and the length of the blackouts are gradually decreasing."
