After 10 months of secret dialogue with Afghanistan's Taliban insurgents, senior US officials say the talks have reached a critical juncture and they will soon know whether a breakthrough is possible, leading to peace talks whose ultimate goal is to end the Afghan war.
As part of the accelerating, high-stakes diplomacy, Reuters has learned, the United States is considering the transfer of an unspecified number of Taliban prisoners from the Guantanamo Bay military prison into Afghan government custody.
It has asked representatives of the Taliban to match that confidence-building measure with some of their own. Those could include a denunciation of international terrorism and a public willingness to enter formal political talks with the government headed by Afghan President Hamid Karzai.
The officials acknowledged that the Afghanistan diplomacy, which has reached a delicate stage in recent weeks, remains a long shot. Among the complications: US troops are drawing down and will be mostly gone by the end of 2014, potentially reducing the incentive for the Taliban to negotiate.
Still, the senior officials, all of whom insisted on anonymity to share new details of the mostly secret effort, suggested it has been a much larger piece of President Barack Obama's Afghanistan policy than is publicly known.
US officials have held about half a dozen meetings with their insurgent contacts, mostly in Germany and Doha with representatives of Mullah Omar, leader of the Taliban's Quetta Shura, the officials said.
The stakes in the diplomatic effort could not be higher.
Failure would likely condemn Afghanistan to continued conflict, perhaps even civil war, after NATO troops finish turning security over to Karzai's weak government by the end of 2014.
Success would mean a political end to the war and the possibility that parts of the Taliban - some hardliners seem likely to reject the talks - could be reconciled.
The effort is now at a pivot point.
"We imagine that we're on the edge of passing into the next phase. Which is actually deciding that we've got a viable channel and being in a position to deliver" on mutual confidence-building measures, said a senior US official.
While some US-Taliban contacts have been previously reported, the extent of the underlying diplomacy and the possible prisoner transfer have not been made public until now.
There are slightly fewer that 20 Afghan citizens at Guantanamo, according to various accountings. It is not known which ones might be transferred, nor what assurances the White House has that the Karzai government would keep them in its custody.
Guantanamo detainees have been released to foreign governments - and sometimes set free by them - before. But the transfer as part of a diplomatic negotiation appears unprecedented.
The reconciliation effort, which has already faced setbacks including a supposed Taliban envoy who turned out to be an imposter, faces hurdles on multiple fronts, the US officials acknowledged.
They include splits within the Taliban; suspicion from Karzai and his advisers; and Pakistan's insistence on playing a major, even dominating, role in Afghanistan's future.
Obama will likely face criticism, including from Republican presidential candidates, for dealing with an insurgent group that has killed US soldiers and advocates a strict Islamic form of government.
But US officials say that the Afghan war, like others before it, will ultimately end in a negotiated settlement.
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