On a balmy December Satur-day in the southern Afghan city of Jalalabad, Zalmay Khalilzad stood before an assembly of farmers. The weather was perfect for planting and the US envoy to Afghanistan had come, armed with a blunt warning and 500kg of wheat seed, to persuade them to grow something other than opium poppies.

"Illegal drugs pose a mortal threat to Afghanistan's future," Mr Khalilzad told the crowd of 150 farmers in a garden of tangerine trees and tall palms. "Corruption follows illegal drugs as surely as night follows day."