Exporters said industrial action could interrupt supplies although commodity analysts said they expected any disruption to be short lived.

Cocoa prices rose sharply in London on Monday as the threat emerged.

Price dispute

Unions said they would launch a wave of industrial action on 18 October unless the farmgate price for cocoa between October and December was set at 500 CFA francs per kg..

The West African country is responsible for 40% of the world's cocoa production, producing about 1.4m beans a year.

Unions earlier rejected a price of 390 CFA francs ($0.74) a kg, set by industry association Coffee and Cocoa Bourse.

Koffi Kanga, a vice-president with the Syprocafcaoci union, said the strike was being supported by 12 farmers' unions and a majority of growers' co-operatives.

"We have decided to launch a general strike from 18 October to call for a guaranteed price," he told Reuters.

"We are going to block the ports and prevent cocoa coming out of the towns and villages producing cocoa."

The industry price is merely indicative, allowing buyers to purchase beans at far lower prices.

This happened frequently during the last selling season, angering farmers and spurring them to seek a fixed price.

However, exporters argue that the suggested price is too high.

"This price is not realistic," said Stephane Chaudron, from Cocaf Ivoire, told Reuters.

"It is going to slow arrivals at the port because it will take a while for growers to agree to sell below this price."

Fears of a dispute sent cocoa prices soaring to a two week high on London commodity markets.