Danish instructors have been training Ukrainian recruits in the East of England region last month
Ukrainian President Volodymyr Zelensky signed a bill lowering the military mobilization age for two years from 27 to 25 years.
Kiev faced heavy battlefield losses after two years of war, while Russia benefited from a significant advantage in manpower.
This step will allow Ukraine to call on more people to replenish its reserves, after the number of volunteers decreased.
Although deputies voted on the bill in May 2023, it did not enter into force because Zelensky did not sign it.
It was not immediately clear what prompted the president to sign the bill on Tuesday, but he has previously warned of plans that could force Russia to launch an attack in the spring or summer of this year.
Zelensky's signing of the bill may signal Ukraine's efforts to build strong defensive fortifications in preparation for a Russian attack.
Ukrainian forces hoped to regain large areas of territory controlled by Russia, as well as cut off Russian supply lines to the Crimean Peninsula.
But lacking air superiority and facing formidable Russian defences, the Kiev counteroffensive has stalled with the onset of winter, and there are fears that Russian forces may overtake Ukraine.
Last year, Ukrainian General Oleksandr Tarnavsky warned that forces had already been forced to scale back some military operations due to a decline in foreign aid.
Ukraine relies heavily on Western supplies, especially on shipments of long-range missiles and air defense systems. However, billions of pounds in US and EU aid have been put on hold amid political rows.
Russian President Vladimir Putin said that more than 600,000 of his forces are fighting in Ukraine, but he did not reveal the number of deaths there.
A secret US intelligence report released in December estimated that 315,000 Russian soldiers had been killed or wounded since the war began — which it said was roughly 90% of Russian military personnel at the start of the invasion.
In February, Zelensky said that 31,000 Ukrainian soldiers had been killed since the start of the war, but US officials estimated the number of Ukrainian soldiers killed at at least 70,000 and as many as 120,000 wounded.
“Infuriatingly humble analyst. Bacon maven. Proud food specialist. Certified reader. Avid writer. Zombie advocate. Incurable problem solver.”