South Africa’s Chamber of Mines, which negotiates with the trade unions on behalf of the industry’s employers on pay, said on Monday it could not sign an agreement with the Solidarity union in the gold sector because the final offer was conditional on all unions accepting it.

Solidarity, which mostly represents skilled workers and supervisors, said earlier that it had accepted the offer for wage increases of between 4.8 and 6 percent for its members.

But a chamber spokeswoman said that it had “consistently made the point that its final offer was conditional on all four unions accepting such offer. No agreement can therefore exist between Solidarity and the Chamber.”

The largest unions in the sector – the National Union of Mineworkers and the Association of Mineworkers and Construction Union – declared disputes with gold producers on Thursday after wage talks reached an impasse.

Their negotiations with the gold firms will now be handled by a government mediator, a necessary regulatory step before the union members can go on strike.

The talks are with Harmony Gold, AngloGold Ashanti Sibanye Gold and a smaller producer.

The positions of the two sides are wide apart, with the employers’ complaining of falling prices and rising costs while the unions want big pay increases to close what they say is the “apartheid wage gap” – the disparities that persist between the black workforce and white management two decades after white rule ended.