West 'should have talked to Taliban'
Gen Nick Carter said it would have been much easier to find a political solution when they were on the run.
His comments in the Guardian come days after attempts to bring the Taliban to the negotiating table stalled.
Gen Carter also warned Afghan forces would need military and financial support after troops leave in 2014.
The Kabul government would have only shaky control over some areas, he said.
Negotiation attempts
A major conference on the future of Afghanistan held in Bonn, Germany, over a decade ago did not include the defeated Taliban former government of Afghanistan.
Gen Carter, deputy commander of the Nato-led coalition, acknowledged it was easy to be wise with the benefit of hindsight but added: "Back in 2002, the Taliban were on the run.
"I think that at that stage, if we had been very prescient, we might have spotted that a final political solution to what started in 2001, from our perspective, would have involved getting all Afghans to sit at the table and talk about their future.
"The problems that we have been encountering over the period since then are essentially political problems, and political problems are only ever solved by people talking to each other."
Last week, US Secretary of State John Kerry expressed caution over whether peace talks on Afghanistan with the Taliban could take place.
A row over the status of a Taliban office in Qatar's capital Doha has overshadowed efforts to start peace negotiations there.
BBC defence correspondent Caroline Wyatt said the row had simply underlined the diplomatic and practical difficulties that remained for anyone wishing to talk to the Taliban.
Gradual withdrawal
Gen Carter said he was confident that Nato's handover of security to Afghan forces would eventually bring the Taliban to the negotiating table.
He said that overall the police and army had been shaped into sustainable institutions strong enough to protect a critical presidential election next year and guarantee stability for the majority of the country after Western forces withdrew.
However, he added that the Afghan army and police would still need help in the years to come because they had been built up very quickly.
However, he expressed optimism about Afghanistan's future as long as the US and its allies came through on promises of financial and military support.
Some 8,000 British troops are still serving in Afghanistan, around half of them at Camp Bastion in Helmand province, many of them still mentoring or advising Afghan forces.
Until last year, the UK had 137 bases in Helmand but the gradual withdrawal ahead of the end of combat operations by 2015 means the mission is gradually changing with just 13 bases still operating.
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