The Association of Mineworkers and Construction Union (Amcu) wants to be recognised as the majority union at Lonmin as it now represents over 70% of the workforce at the world's third largest producer of the precious metal. Amcu has threatened to down tools at the mine this week if talks fail.
"The strike has already been decided, the meeting is to try and avert it," Amcu treasurer Jimmy Gama told Reuters on Tuesday.
"If we are unable to reach an agreement today, the notice [to strike] will be served tomorrow," he said. The company has said such action would be deemed an unprotected strike as the matter is set to go to arbitration later this month.
Lonmin's mines were shut for weeks by an illegal strike in 2012 and were the centre of last year's violence in the platinum belt, which saw 34 miners shot dead by police in a single day in the worst security incident since the end of apartheid.
Amcu, which has emerged as the dominant union in the platinum shafts after a bloody turf war with the once unrivalled National Union of Mineworkers (NUM), has also led two brief wildcat strikes at Lonmin this year, most recently last month.
Lonmin said last week it had increased security at its mines, which are only found in South Africa, in response to violence and labour strife.
Workers from both unions are still getting killed. Last week a NUM shop steward was shot dead at a Lonmin mine, weeks after an Amcu organiser was murdered in a tavern.