A substantial international military presence will be needed in Afghanistan for another five years, the head of the Army has said.
General Sir David Richards said there are currently not enough international forces in the country to complete their mission and hand over responsibility for security to the Afghans.
He spoke as the Ministry of Defence confirmed that a British soldier was killed by a blast in southern Afghanistan on Thursday.
The serviceman, from the Royal Military Police, died while on a foot patrol near Gereshk district centre in Helmand Province. The death was the fourth this month, and took the number of British troops who have died since operations in Afghanistan began in October 2001 to 222.
Gen Richards strongly endorsed the strategy drawn up by General Stanley McChrystal, the US commander of international forces in the country, who is calling for an additional 40,000 troops.
"We are in a period of risk where we haven't got enough troops in the round to do what we all know is required. So we need a bridging force to enable us to contain the Taliban while we much more aggressively grow the Afghan army and police," Gen Richards told the BBC.
"If we get it right, our estimation is that by about 2011, 2012, you will see an appreciable improvement and by about 2014 we will ramp down our numbers while they (the Afghans) ramp up and you will start to reduce the overall risk to the operation.
"It is an ambitious target ... but if I'm half right I'd say we've got five years of declining violence as we get that formula right and then we'll go into a supporting role where we continue to do things that are probably beyond the Afghan army - support and logistics, that sort of thing.
"Obviously the civilian effort will probably go on for many, many years beyond that."
