"Plans are in place to reduce the workforce by approximately 1100 roles - 300 contractors and 800 employee roles," Rio Tinto said in a statement overnight.
"In addition, substantial cost reduction programs are being implemented across all Rio Tinto Alcan facilities."
Rio Tinto bought Canadian aluminium group Alcan for $US38.1 billion ($56.87 billion) in 2007.
Rio Tinto postpones $3bn iron ore mine
UAW agrees to make sacrifices