The international community has been hand-holding Afghanistan for long enough and Kabul should now be left to get on with running the country without the west's constant interference, the British ambassador in Kabul has said.

In an interview with the Guardian, Sir Richard Stagg said it was also clear that the Taliban had grown tired of camping across the border in Pakistan and had accepted they needed to be involved in peace and reconciliation talks over the next two years if they were to have any hope of sharing power.

The Foreign Office does not believe the complex obstacles to negotiations are insurmountable, which will give further encouragement to the voices in Whitehall pushing for an acceleration of the British military and civilian withdrawal.Stagg acknowledged that the debate about withdrawal was ongoing and hinted that he believed a faster drawdown was not only possible, but preferable:

"The question is: how fast do you hand over? It's not a gulf of difference. It is a spectrum and it depends on your judgment on the progress we are making. And on the security side we are making good progress.

"The more the people of Afghanistan see their own government stand on its own two feet, the better for everybody. This is not a matter of us cutting and running and disappearing, it is a matter of shifting the nature of our engagement from hand-holding to one which is offering support as needed and required."

He added: "We need to allow [the Afghans] to get on with things more. The international community has been a bit omnipresent in the last decade and we need to move to a different business model in which we are there to provide help and guidance but not there to try to take decisions for them."

The ambassador's remarks chime with those of Nato's secretary general, Anders Fogh Rasmussen, who said on Monday that the retreat of western forces from Afghanistan could come sooner than expected. "If the security situation allows, I would not exclude the possibility that in certain areas you could accelerate the process," Rasmussen said.

Much will depend on a report from Nato's overall commander in Afghanistan, General John Allen, which will be finished within weeks, and the result of the forthcoming US presidential election.

The White House is not expected to make any big decisions on Afghanistan until after polling day on 6 November. If Mitt Romney wins, Nato commanders expect further delays as a new administration gets to grips with the issues. A former ambassador to India, Stagg took over from Sir William Patey in April this year. He said he had been encouraged by the capability of Afghan security forces, but added that one of his aims was to help underpin faith in the country's political system before the presidential elections in 2014.

The British ambassador to Afghanistan, Sir Richard Stagg. Photograph: Fayaz Kabli/Reuters

Stagg warned there is a danger that western countries expect too much from Afghanistan: "We need to be sensible in our ambition. I think wWe should be careful not to expect Afghanistan, which started off from a far, far worse place than its neighbours, to leap-frog to a far more orderly or better-run society than the rest of the region.

"We should help to lay a foundation so that the principles of how the society might evolve are there. The challenge is to have a process by 2014 that is orderly and transparent, and that it leads to a peaceful transition to a new government. Challenge is not a codeword for impossibility. There are still 18 months to go."

Stagg said the Taliban could see a new political infrastructure being created in Kabul, and had begun to realise that if it wanted to shape Afghanistan's future, it needed to be involved now, and not after the election, when it will be too late.

"There is going to be a process of work over the next two years to shape the future Afghan political environment, and I think the Taliban can see that it would be to their disadvantage not to be part of that process. The Taliban have been in exile for over a decade. They would very much like to be back in their own country. And they have now discovered that the Afghan army is an effective force.

"The sense of being able to take charge of the country … I think they realise this is now totally unrealistic. So if you are thinking that the only way forward is the potential to share power, then talking is a sensible way of achieving that outcome. We are seeing more and more signs that the Taliban are moving towards that understanding."

Nato is working towards pulling out all of its combat forces by the end of 2014, although it has not set out a timetable for withdrawal. Earlier this year, Nato military commanders had argued they needed as many troops there as possible for as long as possible, but that view has changed in recent months. The number of so-called "green on blue" attacks, where Afghan soldiers have shot colleagues in Nato's International Security and Assistance Force, has increased sharply this year.

With more than 50 troops killed, including five Britons, trust between the forces has been strained and calls for a substantial withdrawal of forces in 2013 have increased.