In 2013, private equity firm MBK Partners acquired a 100% stake in ING’s life unit for KRW1.84trn (£128m, $166m, €148m) from the Dutch insurance group.
The deadline to sell the firm has been extended prompting speculation MBK may withdraw the sale.
Lead manager of the sale, Morgan Stanley, had planned to wrap up the final bidding process last week but expects to receive bids well into this week.
Hong Kong-based investment manager JD Capital and two other Chinese firms - Taiping Insurance Group and Fosun International - are reportedly in the running to buy ING as part of an expansion into Korea’s financial services market.
However, a delay in the talks have sparked fears there may problems with pushing through the sale, with an MBK Partners official telling Korea’s Yonhap news agency the firm had not ruled out the possibility of pulling out.