Aceh rebels and Indonesian government delegates made a "breakthrough" at peace talks aimed at ending a three-decade insurgency in the tsunami-ravaged province, the Finnish mediator said. Both sides said they made progress toward ending the conflict, but rebels said they were concerned about Indonesian troop deployments in the region. "I would like to describe this as a breakthrough," said former President Martti Ahtisaari, who mediated the third round of negotiations. "We have moved to a very substantive discussion on the issues," he said Saturday, adding that the next round of talks would begin on May 26 in Finland. Aceh rebels have been struggling for 27 years for a separate homeland in the oil- and gas-rich region where more than 12,000 people have been killed.