The US says they have no plans to destroy crops

The move came after a report in Britain's Guardian newspaper, in which villagers in eastern Afghanistan said US forces had secretly tried to wipe out their poppy crops in April under cover of darkness.

US military spokesman Colonel Rodney Davis said: "That's not what we came here to do and it's not in our plans."

Afghanistan is the world's biggest producer of opium, the raw ingredient for heroin.

'Not capable'

"The bottom line is the coalition has not been involved in the use of herbicides or pesticides," Colonel Davis told reporters at Bagram air base near Kabul.

"The coalition doesn't have helicopters capable of spraying herbicides or pesticides as some have claimed."

He said after extensive checks the US military were able to confirm that they do not have any forces stationed in the region where the chemicals are alleged to have been used.

The Guardian reported that the herbicide spraying had taken place in the Zafar Khel region of eastern Afghanistan.

Since the fall of the Taleban in 2001, Afghanistan has reclaimed its position as the world's top producer of opium.