HAVANA, March 3 (Reuters)—Cuba may soon join a growing list of countries shutting down nickel plants in the face of slumping prices, sources close to the industry said this week, in the latest indication the international economic crisis has begun to bite. Unrefined nickel and cobalt production at two state-run processing plants are under review due to their inefficiencies. "With prices below $10,000 per tonne and an average 117 barrels of fuel oil needed to produce a tonne for market, it is only logical they would be considering cutting back," a foreign businessman said Tuesday, asking his name not be used. Cutbacks are being considered at two state run plants.