Samsung SDI will likely have to sell an additional 500 billion won worth of shares in sister firm Samsung C&T Corporation by the third quarter of next year at the latest.

The Fair Trade Commission announced Thursday it is tightening regulations on share cross-holding between affiliated companies in a conglomerate.

Under the original guidelines applied in the 2015 merger between Samsung C&T and Cheil Industries, Samsung SDI was only ordered to dispose of five million Samsung C&T shares.

The commission has stopped short of specifying exactly how many more shares Samsung SDI will have to shed, but the number is expected to be around four million shares.