Though not publicised, negotiations have been under way for more than a month to secure a strategic partnership agreement which would include an American presence beyond the end of 2014 – the agreed date for all 130,000 combat troops to leave — despite continuing public debate in Washington and among other members of the 49-nation coalition fighting in Afghanistan about the speed of the withdrawal.
American officials admit that although Hillary Clinton, the US secretary of state, recently said Washington did not want any "permanent" bases in Afghanistan, her phrasing allows a variety of possible arrangements.
"There are US troops in various countries for some considerable lengths of time which are not there permanently," a US official told the Guardian.
British troops, Nato officials say, will also remain in Afghanistan long past the end of 2014, largely in training or mentoring roles.
Although they will not be "combat troops" that does not mean they will not take part in combat. Mentors could regularly fight alongside Afghan troops, for example.
Senior Nato officials also predict that the insurgency in Afghanistan will continue after 2014.
There are at least five bases in Afghanistan which are likely candidates to house large contingents of American special forces, intelligence operatives, surveillance equipment and military hardware post-2014. In the heart of one of the most unstable regions in the world and close to the borders of Pakistan, Iran and China, as well as to central Asia and the Persian Gulf, the bases would be rare strategic assets.
News of the US-Afghan talks has sparked deep concern among powers in the region and beyond. Russia and India are understood to have made their concerns about a long-term US presence known to both Washington and Kabul. China, which has pursued a policy of strict non-intervention beyond economic affairs in Afghanistan, has also made its disquiet clear. During a recent visit, senior Pakistani officials were reported to have tried to convince their Afghan counterparts to look to China as a strategic partner, not the US.
American negotiators will arrive later this month in Kabul for a new round of talks. The Afghans rejected the Americans' first draft of a strategic partnership agreement in its entirety, preferring to draft their own proposal. This was submitted to Washington two weeks ago. The US draft was "vaguely formulated", one Afghan official told the Guardian.
Afghan negotiators are now preparing detailed annexes to their own proposal which lists specific demands.
The Afghans are playing a delicate game, however. President Hamid Karzai and senior officials see an enduring American presence and broader strategic relationship as essential, in part to protect Afghanistan from its neighbours.
"We are facing a common threat in international terrorist networks. They are not only a threat to Afghanistan but to the west. We want a partnership that brings regional countries together, not divides them," said Rangin Spanta, the Afghan national security adviser and the lead Afghan negotiator on the partnership.
Dr Ashraf Ghani, a former presidential candidate and one of the negotiators, said that, although Nato and the US consider a stable Afghanistan to be essential to their main strategic aim of disrupting and defeating al-Qaida, a "prosperous Afghanistan" was a lesser priority. "It is our goal, not necessarily theirs," he said.
Though Ghani stressed "consensus on core issues", big disagreements remain.
One is whether the Americans will equip an Afghan air force. Karzai is understood to have asked for fully capable modern combat jet aircraft. This has been ruled out by the Americans on grounds of cost and fear of destabilising the region.
Another is the question of US troops launching operations outside Afghanistan from bases in the country. From Afghanistan, American military power could easily be deployed into Iran or Pakistan post-2014. Helicopters took off from Afghanistan for the recent raid which killed Osama bin Laden.
"We will never allow Afghan soil to be used [for operations] against a third party," said Spanta, Afghanistan's national security adviser.
A third contentious issue is the legal basis on which troops might remain. Afghan officials are keen that any foreign forces in their country are subject to their laws. The Afghans also want to have ultimate authority over foreign troops' use and deployment.
"There should be no parallel decision-making structures ... All has to be in accordance with our sovereignty and constitution," Spanta said.
Nor do the two sides agree over the pace of negotiations. The US want to have agreement by early summer, before President Barack Obama's expected announcement on troop withdrawals. This is "simply not possible," the Afghan official said.
There are concerns too that concluding a strategic partnership agreement could also clash with efforts to find an inclusive political settlement to end the conflict with the Taliban. A "series of conversations" with senior insurgent figures are under way, one Afghan minister has told the Guardian.
A European diplomat in Kabul said: "It is difficult to imagine the Taliban being happy with US bases [in Afghanistan] for the foreseeable future."
Senior Nato officials argue that a permanent international military presence will demonstrate to insurgents that the west is not going to abandon Afghanistan and encourage them to talk rather than fight.
The Afghan-American negotiations come amid a scramble among regional powers to be positioned for what senior US officers are now describing as the "out years".
Mark Sedwill, the Nato senior civilian representative in Afghanistan, recently spoke of the threat of a "Great Game 3.0" in the region, referring to the bloody and destabilising conflict between Russia, Britain and others in south west Asia in the 19th century.
Afghanistan has a history of being exploited by — or playing off — major powers. This, Dr Ghani insisted, was not "a vision for the 21st century". Instead, he said, Afghanistan could become the "economic roundabout" of Asia.