South Africa’s National Union of Mineworkers (NUM) on Friday accused De Beers of reneging on a deal for a 12 percent wage increase, Reuters reported. The union said on Thursday that De Beers had agreed to the wage increase but said later that the mining firm then changed its proposal.

According to a statement, NUM is now demanding a 13.5 percent wage raise. “We are folding our sleeves for a big fight. De Beers will never be allowed to successfully lie to workers. We will take the fight to them,” commented NUM Chief Negotiator Peter Bailey. “It is either 13.5 percent or it is war.”

De Beers responded by saying that the union had released news on a not-yet-finalized agreement. “The NUM put out an announcement of an agreement that was not really in place and they have since retracted it,” a De Beers spokesperson, Tom Tweedy, was quoted as saying. 

NUM has also declared a dispute with South Africa’s arbitration authority, which is a prerequisite to calling any strike.