Russia is seeking to change its age criteria and introduce "wider military conscription", according to the Ministry of Defence (MOD).
In its latest defence intelligence update on Twitter, the MOD said Russian parliamentarians had "introduced a bill to change the age bracket for conscription to men aged 21-30 years, from the current 18-27. The law is likely to be passed and would come into force in January 2024."
Russia has already mobilised former serving soldiers to return to the ranks and the MoD said although conscripts are "officially" barred from serving in Ukraine, it estimated "at least hundreds have probably served through administrative mix-ups or after being coerced".
The intelligence update added: "The authorities are highly likely changing the age bracket to bolster troop numbers by ensuring that students are eventually forced to serve. Even if Russia continues to refrain from deploying conscripts in the war, extra conscripts will free up a greater proportion of professional soldiers to fight."
This comes as Britain welcomed the issuing by the International Criminal Court (ICC), of an arrest warrant for Russian President Vladimir Putin for war crimes in Ukraine.
The Hague-based ICC said it was issuing the warrant for the arrest of the Russian leader over the alleged abduction and deportation of thousands of Ukrainian children to Russia.
The charges were immediately dismissed by the Kremlin – which does not recognise the ICC – as "legally void".