On Thursday evening, Volodymyr Zelensky, the Ukrainian president, warned that it was now only a matter of days before up to 13,000 North Korean soldiers entered the war and pleaded to the West for a strong response.

“Putin is checking the reaction of the West, checking the reaction of Nato countries, the reaction of South Korea,” he said of the North Korean troop deployment.

The assessment that Pyongyang would soon enter the war was backed up by US officials who have reportedly turned to China to try to use its influence to restrain Kim.

Western analysts have said that the quality of North Korean soldiers sent to fight for Russia will be poor and that communication with Russian units will be complicated.

The North Korean soldiers are likely to be conscripts with no Russian language skills and no combat experience, used by the Kremlin as cannon fodder for its mass infantry tactics.