The Association of Mineworkers and Construction Union (AMCU) has been negotiating with the country's biggest platinum miners since June, and in October referred the dispute with Amplats and Sibanye-Stillwater to a government dispute resolution body.

The signing ceremony will take place in Muldersdrift, a town in South Africa's platinum mining heartlands 30 kms (20 miles) northwest of Johannesburg at 0800 GMT on Wednesday, AMCU said.

(Reporting by Helen Reid; Editing by Jon Boyle)