US Secretary of State John Kerry began a difficult mission to mediate an end to the political crisis in Afghanistan Friday, warning that a bitter dispute over presidential polls threatened the country's future.
"Obviously we are at a very critical moment for Afghanistan," Kerry said as he met the head of the UN assistance mission in the country, Jan Kubis.
"The election legitimacy hangs in the balance. The future potential of the transition hangs in the balance, so we have a lot of work to do."
The top US diplomat also met outgoing President Hamid Karzai, and then former World Bank economist Ashraf Ghani, who is well ahead in the preliminary results of last month's second round run-off.
In a swift boost for Kerry's diplomacy, Ghani threw his backing behind US calls for a wide audit of the elections, amid accusations by his rival Abdullah Abdullah of massive fraud.
"Our commitment is to ensure that the election process enjoys the integrity and the legitimacy of the people of Afghanistan and the world," Ghani told reporters as he was welcomed to the heavily fortified US embassy in Kabul.
"Therefore we believe in the most intensive and extensive audit possible to restore faith."
Ghani said he and his supporters were committed to "an inclusive government. A government that could represent all of Afghans, and serve every Afghan citizen in the manner that every Afghan deserves according to the constitution".
Kerry, who will meet Abdullah later on Friday, stressed "no-one is declaring victory at this time. The results are yet to be finalised".
The stakes could not be higher, as the next president will have to steer the war-torn country as international troops withdraw, leaving Afghan forces to fight a bloody, stubbornly resilient Taliban insurgency.
"Our hopes are that there is a road that can be found that will provide that capacity for the questions to be answered, for people's doubts to be satisfied and hopefully for a future to be defined," Kerry said.
But he warned that was not "an automatic at this point".
Preliminary results have put Ghani in the lead, but Abdullah, who has already once lost a presidential bid in controversial circumstances, has declared himself the true winner, saying massive fraud robbed him of victory.
The election stand-off has sparked fears that protests could spiral into ethnic violence -- and even lead to a return of the fighting between warlords that ravaged Afghanistan during the 1992-1996 civil war.
Need for thorough audit
The US was "going to push for the very best, most credible, most transparent and most broadly accepted outcome that we can under the circumstances," a senior US official said.
Auditors may look at districts with a very high turnout, or a perfectly round number of recorded votes, or where the number of women voters outnumbered men, "which in the Afghan context seems like an unlikely outcome".
A statement from Karzai's office said Kubis had presented a UN plan late Thursday to audit some 8,000 ballot boxes, representing 43 per cent of the total votes -- or around 3.5 million votes.
UN officials have said a full audit of the results could take up to two weeks, but some Afghan officials are pressing to stick by an election calendar that would see the new president inaugurated on August 2.
Amid protests and political turmoil, the United States has warned both candidates that any attempted power grab will lead to an immediate cut in billions of dollars of annual aid.
After more than 13 years of war following the 2001 US invasion to oust the hardline Taliban regime, President Barack Obama has said all American forces will be withdrawn by the end of 2016.
The 30,000 US troops on the ground will be whittled down to 9,800 next year.
The Obama administration is also desperately waiting for Afghan leaders to sign a bilateral pact governing the presence of US forces in the country beyond this year.
Karzai walked away from the deal, but both presidential candidates have said that they would sign it.