LONDON (REUTERS) - Afghanistan is spiralling into a failed state and a civil war in which militant groups such as Al-Qaeda will thrive and likely pose a threat again to the West, Britain's Defence Minister said on Friday (Aug 13).

After a 20-year war in Afghanistan, the United States has withdrawn most of its troops, allowing Taleban forces to sweep across the country in what diplomats have cast as a humiliation for the world's pre-eminent superpower.

"I'm absolutely worried that failed states are breeding grounds for those types of people," Defence Secretary Ben Wallace told Sky News when asked about Afghanistan.

"Al-Qaeda will probably come back."

Mr Wallace had told the BBC: "Britain found that out in the 1830s, that it is a country led by warlords and led by different provinces and tribes, and you end up, if you're not very careful, in a civil war, and I think we are heading towards a civil war."

Mr Wallace cautioned that the Taleban was not a single entity but rather a title that encompassed "all sorts of different interests".

The speed of the Taleban advance has shocked the Afghan government and its Western allies.

The Taleban controlled most of Afghanistan from 1996 until 2001, when it was ousted for harbouring Al-Qaeda chief Osama bin Laden after the Sept 11 attacks on the United States.

Mr Wallace said the West had to understand that it could not instantly fix countries such as Afghanistan, but should manage situations.

He said that if the Taleban started to harbour Al-Qaeda, then "we could be back".

Mr Wallace said that Afghanistan's second-biggest city of Kandahar and the town of Lashkar Gah were "pretty much now in the hands of the Taleban".