"A protracted strike will undermine the long-term viability of Northam and could threaten jobs," the company said in a letter published in the Business Day newspaper on Monday to Frans Baleni, the General Secretary of the National Union of Mineworkers (NUM).
Northam, which produces around 1 000 ounces of platinum group metals a day, is losing R14m a day in revenue, with the strike costing it over R200m so far.
"The company is not the only loser here: striking employees have so far lost R30m in wages," the company said.
Northam also said its latest offer for wage hikes of between 8% and 9% - well above inflation of 5.5% - was its final one.
NUM has been pushing for increases of up to around 40%.
Northam is one of the few platinum producers where NUM still represents most of the workers after it lost tens of thousands of members last year to the hardline Association of Mineworkers and Construction Union (Amcu) in a bloody turf war that left dozens of people dead and sparked a wave of wildcat strikes.
NUM's tough stance with Northam partly stems from its need to counteract Amcu's militancy and retain its remaining members.
Amcu remains in wage talks with the world's top three producers of the precious metal, Anglo American Platinum [JSE:AMS], Impala Platinum [JSE:IMP] and Lonmin [JSE:LON], where it has majority representation at all three companies.