According to union Sintracarbon, the accord was presented to workers from Monday to Wednesday last week and, following majority approval, the drafting of a final document began on Thursday.

Expected to be signed and finalised by Friday, discussions and drafting have continued because of disagreement over specific wording in the document, according to a union statement.

Workers chose a three-year offer as opposed to another two-year choice on the table because the longer agreement would give them a bonus of about $7000, Reuters reports.

That deal gives workers a pay increase of 5.1% in the first year and then other increments adjusted for inflation in the following two years.

Before the strike began, the company offered a rise of 5% while the union asked for 7%.

Cerrejon is Colombia’s biggest coal mine, producing 100,000 tons of coal a day. It has not produced any coal since the strike began on February 7.

The mine is owned by Xstrata, Anglo American and BHP Billiton.

Colombia is the world’s fourth-largest coal exporter. It produced 87 million metric tons in 2011, falling short of a 100Mt goal, in part because of a 25-day coal railway strike that forced output target cutbacks.