The two-day event will bring together some 400 politicians, economists, business people and scholars from Europe and the world.
Croatia's Foreign Minister Gordan Jandrokovic confirmed his arrival at the event.
Some of the high-profile participants are former US State Secretary Colin Powell, Arab League Secretary-General Amr Moussa, Indian Foreign Minister Preneet Kaur, Canadian Defence Minister Peter Gordon MacKay, Belgian Prime Minister Yves Leterme, European Union representatives and officials from the region.
The forum will be opened on Sunday afternoon by Slovenian officials -- President Danilo Tuerk, Prime Minister Borut Pahor and Foreign Minister Samuel Zbogar.
One of the panel discussions, to be moderated by Tim Juduh, a reporter for The Economist, will be on connecting western Balkan countries in the spheres of the economy, power and transport.