Leaders of a union that operates Colombia's main coal railway met Wednesday to decide exactly how to respond to a unanimous court ruling that declaring its three-week strike illegal.

The Bogota-based three-judge panel ruled that the 23-day strike by the Sintraime union, which has shut off more than 50 percent of coal exports from Colombia, was illegal, Reuters said. The nation is the world's No.4 coal exporter and has seen its exports cut by about four million metric tons since the job action against the railway operated by Fenoco. 

Drummond International, which is 20 percent-owned by Japan's Itochu, Glencore's Prodeco unit and a Goldman Sachs affiliate all depend on the railway to move coal to market. Colombian coal production also has been hit by a walkout at Prodeco's La Jagua mine.

Shortly after Tuesday's court decision, union officials vowed to appeal the decision. On Monday, union officials declared a vote by their members to end the strike illegal and promised to continue the walkout.

The strike is costing Colombia's government about $1.2 million per day in royalties, Reuters said.