Posco told Dow Jones yesterday it was interested in founder Ken Talbot's 19.8% stake, but as yet had not had discussions with the Queensland miner.
Last month India's ArcelorMittal took a 14.9% stake in Macarthur, 4.3% of which came from Talbot's holding in the company.
Yesterday Macarthur said that talks with ArcelorMittal are continuing.
Already another foreigner has an interest in Macarthur, with China's Citic Resources holding a 17.7% stake in the miner.
Posco has worked to secure its raw material supply through taking stakes in Australian mines, including Carborough Downs (5%), Foxleigh (20%) and Glennies Creek (5%). It also has links with explorer Cockatoo Coal.