The main trade union for South Africa's platinum miners on Sunday called a strike over pay at sites run by the three top world producers of the precious metal.
The Association of Mineworkers and Construction Union (AMCU) said it expected 100,000 workers at Anglo American Platinum, Impala Platinum and Lonmin to down tools from Thursday.
Impromptu strikes are frequent in South Africa and are often linked to union rivalry, working conditions and wages.
The industry is still recovering from a wave of violent strikes in 2012, including a Lonmin strike where 34 workers were shot dead by police on a single day in August.
The hardline AMCU union had earlier said it would call a strike at Impala and Lonmin to demand a minimum monthly salary of 12,500 rand ($1,440), but that talks with Anglo American were continuing.
AMCU claims the current entry-level wage is around 5,000 rand, although platinum producers give higher figures.
"We are going to serve them the 48 hours' notice all the same day, tomorrow, and the strike will commence on the Thursday in the morning," treasurer Jimmy Gama told AFP on Sunday.
Sector-wide strikes would cripple world platinum supply, since South Africa produces 80 percent of the global output.
The 100,000-member union also said this week it will strike at gold mines where it is the minority labour grouping.
It has rejected eight-percent wage increases offered by platinum and gold producers.
Following official processes for strikes marks a change from AMCU's past practice of wildcat stoppages since it gained prominence on the platinum belt two years ago.
It wrested control of platinum mines from the government-linked National Union of Mineworkers then with promises of dramatic salary increases.
Gama said the upcoming strike would be conducted peacefully.
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