By Luis Jaime Acosta
BOGOTA, Jan 9 (Reuters) - Union workers at Colombia's largest coal mine, Cerrejon, could strike if disagreements at negotiations for wages and benefits are not resolved by Jan. 19, the main union's president said on Tuesday.
A strike at the Cerrejon mine, which produces 32 million tonnes of coal a year, or about 37 percent of Colombia's total output, could reduce production and overseas sales from the world's fifth-largest exporting nation of the mineral.
"It is very possible that we won't reach agreement," Aldo Amaya, president of the Sintracarbon union, told Reuters. "We are organizing everything because it's probable there will be a strike at Cerrejon."
The union has demanded a 12 percent wage increase in the first year, while the company has offered 5.2 percent as well as a bonus to each employee and health and education benefits.
Cerrejon's offer is above the 4.09 percent inflation for last year, but Amaya said its offer does not meet union expectations given strong coal prices in recent months.
If union members vote to strike, the stoppage could begin three days after. The last strike in Cerrejon, which produces coal at its open pit mine in La Guajira, northern Colombia, was in February 2013 and lasted 32 days.
Cerrejon, which belongs in equal parts to BHP Billiton BHP.AX BLT.L , Anglo American AAL.L and Glencore GLEN.L , said on its website that it is confident it will reach a deal with the union. It said its offer is fair and based on projections for a difficult year in international coal markets.
Colombia's coal output fell 8.1 percent to 21.5 million tonnes in the third quarter from a year earlier. The sector produced 65.1 million tonnes of coal in the nine-month period, 4.4 percent lower than for the same period a year earlier.