KYIV, Aug 24 (AFP) - Six months into Russia's invasion, Ukrainian officials are drawing up plans to make sure Russian President Vladimir Putin and his top military commanders will be tried for launching the war.

The plan for a special international tribunal to investigate Russia's alleged "crime of aggression" is being spearheaded by Andrii Smirnov, deputy head of Ukraine's presidential administration.

The definition of the crime of aggression was adopted in the 2010 Rome Statute, and the similar notion of "crime against peace" was used in trials in Nuremberg and Tokyo after the Second World War.

The International Criminal Court, which has been trying the gravest crimes for the past 20 years, is already investigating war crimes, crimes against humanity and genocide in Ukraine.

But it cannot look into accusations of aggression because neither Ukraine nor Russia have ratified the Rome Statute.

This court is "the only way to make sure that the criminals who started the Ukraine war are held accountable quickly," Smirnov told AFP.

"The world has a short memory. That's why I would like this tribunal to start working next year."

Ukraine knows that the accused will not be present, but this tribunal "will serve to make sure that these people are labelled as criminals, and that they cannot travel in the civilized world," he said.