Sintramienergetica union vice president Edgar Munoz told Reuters that the parties were still trying to come to a pay deal, but the pre-agreed strike action could become a reality as early as late Tuesday or sometime Wednesday local time.

He said that no progress had been made on the company’s latest offer of 4.5% in pay raises, nor had any deals been made on the hundreds of port workers who could be out of a job in a round of job cuts next year following an improvement project that would make them redundant.

Talks went late into the night Monday, and no information was available on the sit-downs by Tuesday afternoon US time.

“From today we are on maximum alert ... [a strike] could be from today or tomorrow,” Munoz told the news service.

Should the Drummond strike start, the impact could hit quickly and cut output from the world’s fourth-largest export country by as much as one-third.

Drummond is one of the Andean nation’s biggest producers next to Cerrejon.

The timing also compounds the problem, as many purchases are seeking to order winter supplies, which has increased demand, and a prolonged stoppage could have a global ripple effect.

Munoz told Reuters that Labor Minister Rafael Pardo Rueda was again a part of negotiations on Tuesday, his second day at the table. The decision to bring in the official underscores the potential stakes at play in the situation.

It would not be the first strike for the coal-rich country in 2013. In February hundreds took part in a month-long strike at the Cerrejon complex for a similar cause.

The Sintramienergetica union has demanded a pay rise of 10.7% for this year and smaller increments in coming years.

Drummond’s largest offer to date was 4.5% plus incremental jumps in subsequent years to follow inflation.

Colombia is South America’s largest coal producing nation.