An international office to investigate Russia over its invasion of Ukraine opens on Monday in The Hague, in the first step towards a possible tribunal for Moscow's leadership.
The International Centre for the Prosecution of the Crime of Aggression (ICPA) features prosecutors from Kyiv, the European Union, the United States and the International Criminal Court (ICC).
It will investigate and gather evidence in a move seen as an interim step before the creation of a special tribunal that could bring Kremlin officials to justice for starting the Ukraine war.
Senior officials will hold a press conference at the ICPA at the headquarters of the EU's judicial agency, Eurojust, scheduled to begin at 11:15 am (0915 GMT), Eurojust said in a statement.
They include Ukrainian prosecutor general Andriy Kostin, ICC prosecutor Karim Khan, US Assistant Attorney General Kenneth Polite and EU Justice Commissioner Didier Reynders, the statement added.
Calls for a special tribunal on Ukraine have mounted because the ICC, a war crimes court which is also based in The Hague, has no mandate to investigate the broader crime of aggression.
The ICC is probing more specific war crimes and crimes against humanity in Ukraine, and issued an arrest warrant for Russian President Vladimir Putin in March over alleged child deportations.
Kyiv has been pushing for a special tribunal since the discovery of hundreds of bodies after Russian troops withdrew from the town of Bucha near the Ukrainian capital in April 2022.
International support has grown steadily, and the European Commission then announced the creation of the ICPA in February.
Brussels said the centre had the "ultimate aim of prosecuting those responsible for the invasion" of Ukraine.
The involvement of the United States has added weight to the push for a special court, despite the fact that Washington still refuses to join the ICC.
During a visit to The Hague in June, US Attorney General Merrick Garland appointed a special prosecutor for the crime of the aggression, Jessica Kim, as its representative to the ICPA.
But the complex question of how such a court would work remains unresolved.
Ukraine favours obtaining a resolution from the UN General Assembly.
But some of Kyiv's Western backers fear it would lack international backing, arguing instead for a hybrid court with Ukrainian and foreign judges.
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