US Secretary of State John Kerry arrived in Afghanistan Friday on a key mission to try to quell tensions over disputed presidential polls, which have triggered fears of violence and ethnic unrest.
Kerry, who landed on a pre-dawn, unannounced visit, had earlier said Afghanistan faces a "critical moment" as Abdullah Abdullah and Ashraf Ghani wrangle to take up the reins while international forces withdraw following more than a decade of war.
Preliminary results from a second round run-off have put Ghani in the lead, but Abdullah, who has already once lost a presidential bid, has declared himself the true winner, saying massive fraud robbed him of victory.
The election stand-off has sparked concern 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.
Without backing either candidate, Kerry was to meet Friday with outgoing President Hamid Karzai as well as both presidential hopefuls, UN officials and possibly members of the independent election commission.
He will be pressing both candidates to accept a thorough audit of results in some key areas which have raised concerns.
The top goal was to try to "finalise the election", a senior US administration official told reporters flying in with Kerry from Beijing.
"That's going to require a thorough review of all reasonable allegations of fraud which means doing significant additional audits," the official said, asking not to be named.
State Department press office director Jeff Rathke said in a statement that "while the United States does not support an individual candidate, we do support a credible, transparent and inclusive process that affirms the Afghan people's commitment to democracy".
Washington was also looking to the troubled election process to produce "a president who can bring Afghanistan together and govern effectively", Rathke added in the statement.
- Unrest fears grow -
The United States has warned both candidates that any attempted power grab will lead to an immediate cut in billions of dollars in annual aid to Afghanistan.
Kerry himself, speaking at a press conference after two days of high-stakes talks in Beijing, said that "this is a critical moment for the transition which is essential to the future governance of the country".
After more than 13 years of war following the 2001 US invasion to oust hardline Taliban militants, President Barack Obama has said all American forces will be withdrawn by the end of 2016.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, leaving Afghan security forces in full control of battling a resilient Taliban and Al-Qaeda insurgency.
Eight million votes were cast in the election, and preliminary results showed Ghani garnered an estimated 56 percent, while Abdullah, who had been seen as the front-runner, got some 43 percent -- a gap of around one million votes.
"The problem is that both candidates have acknowledged and agreed even before those results were announced that there was wide-spread fraud in this election," the US senior administration official said.
"Our view was that until the candidates were satisfied by the degree of audits that have taken place, there should not have been an announcement of results. And we made that clear."
He also stressed that, according to the US, the preliminary results may or may not reflect the true outcome of the tight vote. The US would not acknowledge any final results until "a satisfactory auditing has taken place".
Both Obama and Kerry have spoken to both presidential rivals by telephone to encourage them to accept an audit, as well as to speak to each other, "something that's not happening", the official said.
There are growing fears in Washington that unless the political transition is successfully achieved, the situation could deteriorate and mirror the chaos in Iraq, where Islamic militants have captured a huge swathe of northern territory.
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.