Peace talks between Indonesian officials and Aceh separatists have run into a "disastrous" hurdle in discussions of political participation, the rebels said, claiming Jakarta had "sabotaged" the process.

"It's going diasastrously," Free Aceh Movement (GAM) political advisor Damien Kingsbury told AFP before a fourth day of talks got under way.

His comments come less than a day after the separatists optimistically announced that the Indonesian government appeared to be willing to concede to their demands for the right to create local political parties that are not controlled by Jakarta.

GAM said late Thursday that it had received a written proposal from Jakarta suggesting how to resolve the issue, and said it acknowledged that Indonesia now "endorses the basic democratic principles of freedom of association regardless of place or number of members".

But later, Kingsbury said Indonesian Justice and Human Rights Minister Hamid Awaluddin made public statements that revealed confidential details of The proposal. He allegedly emphasized an offer from the government to appoint GAM members to political positions instead of going through an electoral process, something the separatists have flatly rejected.

"Such a sweetheart deal for GAM (is) ridiculous and wouldn't allow the inclusion of other parties in Aceh... It's not democratic," Kingsbury said. "They've basically sabotaged the process," he said, adding that he now did not think the parties would be able to reach an agreement on the issue by the time the ongoing round of talks, which have been described as decisive, are scheduled to wrap up on Sunday.

"We thought we were getting towards an agreement (but) now I don't think there's any way of finalizing this time... Awaluddin's comments were not very helpful," he said.

Indonesian Communications Minister and delegate at the talks Sofyan Djalil meanwhile remained upbeat on the prospects of resolving the issue. "We'll find a very good solution for this," he told AFP.

Nearly 15,000 people have been killed since GAM launched its campaign For independence for the western Indonesian province of Aceh in 1976.

While four previous rounds of talks held in the Finnish capital since January have led to few concrete advances towards ending the conflict, hopes Have been high that the current fifth round would lead to a genuine settlement and that a peace treaty could be signed next month.