In London, the main market for cocoa, futures contracts touched ?1,600 ($2,500) a tonne, creeping close to a 17-year high.

On the New York market, prices rose 2.25% to $2,317 per metric ton, the highest since September 1985.

The fighting in Ivory Coast has already disrupted trade and buyers are turning to other growers in the region.

The International Cocoa Organisation has also delayed plans to relocate its headquarters to the capital Abidjan from London.

Cocoa prices have risen 12% since the fighting began in Ivory Coast, which produces about 40% of global supply, on 19 September.

The world's largest cocoa-trading company, ED&F Man Cocoa, has predicted production will be down 4.1% this year, heightening fears demand will outstrip supply for the third year running.

Cocoa farmers in Ghana's important Ashanti growing region are already anticipating a bumper year.

The Ghana Cocoa Board (Cocobod), has already said it would increase farm gate prices to 6.2m cedis ($763) per tonne of beans when it opens sales on Friday.

Ghana, the world's third largest cocoa producer, is the only major grower that still fixes prices.

Cameroon's cocoa farmers have reportedly doubled their earnings after the sharp rise in world prices over the last three weeks.

Cameroon produces only about a tenth of Ivory Coast's one million tonne output.