Britain has sought his extradition from Moscow, but the Kremlin is holding fast against the request, saying that extraditing nationals is against its constitution.
At Wednesday's summit at the White House, further measures were agreed to bring the two sides closer together on issues of global security, including an agreement on extraditing terrorist suspects.
Forcing British courts to match the dates of complex foreign legislation with the dates of similar statutes in Britain would make extraditing even those who have committed what everyone agrees is a crime much more difficult.
Picula told Reuters Del Ponte and Racan would probably seek to speed up the process of tracking down and extraditing war criminals and added that the Croatian judiciary itself would also want to play an active part.
The international police agency Interpol - which has issued arrest notices for all 11 suspects although it admitted their true identities were unclear - issues red notices to seek the arrest of wanted persons with a view to extraditing them.