Sri Lanka's government and Tamil Tiger rebels agreed on Thursday to work out regional autonomy within a federal system in a major breakthrough towards ending a 19-year separatist war.‘‘Both parties have made an unprecedented historic decision,’’ rebel negotiator Anton Balasingham said after four days of Norwegian-brokered peace talks in an Oslo hotel with chief government negotiator G.L. Peiris.The accord on a federal model with limited self-rule for Tamil areas is a big step towards ending the conflict in the island nation in which 64,000 people have died.The rebels last week dropped a key demand for independence for the north and east of the island.The two sides agreed a truce in February and have held three rounds of peace talks in Norway and Thailand.Peiris said the parties would aim for ‘‘extensive powersharing within the framework of one country,’’ evaluating different federal models for the future Sri Lanka.Peiris however added that a final settlement was still far off. The two sides have examined federal models such as that in Canada, where the Francophone province of Quebec sits alongside the English-speaking majority, to help peace and rebuild the shattered Sri Lankan economy. Other models for integration of minorities include Australia, Germany, Switzerland and India.The next two rounds of talks in Thailand in January and February will focus on details of power sharing, Norwegian Deputy Foreign Minister Vidar Helgesen, who hosted the talks, said.(Reuters)