Kabul - Afghanistan's 10-week election crisis entered a risky new stage on Monday when officials started invalidating fraudulent votes in a process likely to bring to a head the bitter dispute raging between the presidential candidates.
The country has been in paralysis since the 14 June election to choose the successor to President Hamid Karzai, who will step down as US-led troops end their 13-year war against Taliban insurgents.
Karzai has insisted the delayed inauguration ceremony must be held on 2 September, imposing a tough deadline that has raised tensions between supporters of poll rivals Ashraf Ghani and Abdullah Abdullah.
The vote was quickly mired in allegations of massive fraud, with Abdullah claiming that he had been denied victory after Ghani was declared ahead on preliminary results.
Democratic keystone
A smooth transition of power was meant to be the democratic keystone of the multi-billion dollar military and civilian aid effort in Afghanistan, but the impasse has emboldened the Taliban and weakened the fragile economy.
An anti-fraud audit of all eight million votes was agreed by both candidates as part of a US-brokered deal to calm tempers as fears rose of a return to the ethnic hatred of the 1990s civil war.
"The IEC today begins the inspections of the audit result in an open session in the presence of national and international observers," Abdul Rehman Hotaki, deputy chairperson of the Independent Election Commission, told reporters.
He said the audit, which has not yet been completed, was a "huge logistical task" but that it would be successful.
Possible angry street protests
Invalidation figures will be published daily by the IEC.
Ghani and Abdullah have also pledged to form a national unity government whoever wins the election, though the details of the power-sharing system have been subject to disagreement between the campaigns.
The US has been pushing for the next president to be inaugurated before a Nato summit starting on 4 September, which should sign off on follow-up support after the coalition's combat mission in Afghanistan ends this year.
The political crisis would worsen sharply if either candidate pulls out of the audit or rejects its outcome, with possible angry street protests in Kabul by aggrieved supporters posing a major challenge to the national security forces.