South Africa's National Union of Mineworkers (NUM) said it will strike at Anglo American's coal unit if the company does not provide more benefits and improved working conditions.
NUM spokesman Lesiba Seshoka said that during a protest march last week, union workers sent a memorandum of demands to Anglo Coal.
"We have given Anglo Coal seven days to respond to the demands and to tell us what processes they will take to act on the demands," Seshoka told Reuters.
"If they do not respond within that period then we will have an indefinite strike action."
The demands include childcare units for female workers and funeral coverage for miners' families.