The Cerrejon impasse is just the latest problem for the world’s fourth-largest coal exporter whose extractive companies have been plagued by increased rebel attacks and labor unrest in recent years.

The strike, with near total union support, will not mean immediate stoppage, however. Under Colombian law, workers cannot walkout the day after the vote. The union seeks a 7% annual wage increase; Cerrejon has offered 5%.

Cerrejon produced 34.6 million metric tons (mt) of coal last year, 4% more than expected and exported 32.8 million mt, 2.5% above its goal.

A U.S.-backed military offensive against Marxist rebels and drug cartels has helped increase security in Colombia while drawing billions in investment, mainly into the oil and mining sectors.