Chocolate eaters are being warned a shortage of cocoa beans could mean a shortage of the sweet treat and an increase in its price.

A declining supply of cocoa beans due to a drought in West Africa will mean the first shortage in three years.

Chocolate manufacturers are warning that with no supply to meet the growing demand the price may rise.

Earlier this year, cocoa grinders cut back on outputs and started using reserves of butter to fill orders from chocolate makers.

The butter is extracted from cocoa bean and is used in around 20 per cent of a chocolate bar.

A powder is also taken from the cocoa bean and used to make products like biscuits and icecream.

New Zealand chocolate maker Whittaker's could not rule out a price increase for their bars here.

National sales manager Matt Whittaker says it won't affect pricing in the short term but if demand outstrips supply the price of cocoa will go up and ultimately chocolate prices will follow, assuming that happens.

Prices are estimated to increase as early as next year by as much as 7.5 per cent or more than $3200 a tonne.

It is estimated cocoa demand will exceed production by 101,000 tonnes this season.

According to a prediction by investment bankers Macquarie Group, the shortage of cocoa beans means global output will drop 2.9 per cent to 3.85 million tonnes, led by smaller harvest in Ivory Coast, Ghana, Indonesia and Nigeria.

These four nations produce 74 per cent of the world's cocoa beans.