(VOVworld) - Talks on a power-sharing deal between Afghanistan's rival presidential candidates Ashraf Ghani and Abdullah Abdullah have collapsed, rekindling fears of ethnic unrest over disputed election results. Under the terms of a deal brokered by US Secretary of State John Kerry, the runner-up in the vote was to name a "chief executive" in a national unity government conceived to keep the lid on political tensions. But the two sides could not agree on the powers of the chief executive. Abdullah Abdullah released another ultimatum over the disputed election results and threatened to withdraw from negotiation to solve the current political deadlock without an audit of votes under UN ground mission’s supervision. The audit of all 8.1 million of votes is scheduled to be completed after September 10.