Union officials Jhon Mendoza and Luis Manuel Mendoza told Bloomberg and Reuters that the union would submit the workers’ proposal to the producer on April 30 with a list of demands, including improved health care, food and housing and education.

The 5000 union workers are also seeking safety changes, including guaranteed benefits for accident victims.

Jhon Mendoza said the union expected to finalize the agreement with Drummond within three weeks.

“Our demands are in line with the existing reality,” he told Bloomberg.

“We want better labor guarantees to compensate for the struggle of the underpaid and abusive mining industry of these multinationals.”

Drummond, Colombia’s second largest coal miner, produced 26 million tonnes in 2012, or about one-third of the country’s total.

Luis Manuel Mendoza told Reuters that the monthly wage demand would be in line with their hourly wages, thus they would be earning the same amount, though he did not indicate why the union was requesting the alteration.

“We don't think that this will imply a higher expense for the company,” he said, adding the producer’s response to their proposal would set the tone for finding an end deal.

"We hope to reach an agreement in 10-15 days but it will all depend on the company's willingness to negotiate.”

US-based Drummond, which restarted its coal exports in March after a three-week government ban on loading operations stemming from a January coal dumping incident, did not release a public statement on Friday.

Colombia is the world’s fourth-largest coal exporter and a large percentage of its tonnage goes to the US and Europe.