Morgan Stanley, the lead manager for South Korean private equity firm MBK Partners, has extended the deadline for final bids to sell ING Life Insurance's Korean unit, a source familiar with the matter said Tuesday.

The move sparked speculations that the bidding could fall apart again or MBK Partners could withdraw its plan to sell its 100-percent stake in the country's fifth-largest life insurer, with 30.3 trillion won ($26 billion) in assets.

Morgan Stanley had planned to conclude the final bidding process on Friday, but it began to receive bids on that day and expects to receive bids this week, the source said.

The extension of the deadline came as some potential buyers put off their decisions on whether to submit a final bid for ING Life's Korean unit.

Three Chinese companies -- Hong Kong-based investment manager JD Capital, Taiping Insurance Group and Fosun International -- are widely expected to submit a final bid for ING Life's Korean unit as they aim to expand into the Korean financial market.

China's Anbang Insurance Group and other companies dropped their bids during preliminary due diligence that began in June.

Another source in the investment banking industry said the failure to conclude the final bidding process after carrying out preliminary due diligence for about 10 weeks, longer than usual, suggests that there could be some problems.

"There is a possibility that the sell-off could fall apart or be withdrawn," the source said.

A senior MBK Partners official did not rule out the possibility that his company could pull out of the sale of its stake in ING Life's Korean unit.

"We may not sell the stake this time if we could not get our desired price," the official said.

The homegrown equity fund hopes to sell its holdings for at least 3 trillion won, according to the sources familiar with the matter.

MBK acquired a 100-percent stake in ING Life's Korean unit for 1.84 trillion won from Dutch insurance group ING in 2013.

If the assets are acquired by a Chinese company, it will mark the third Chinese takeover of a Korean life insurer after Anbang Life's acquisitions of Tongyang Life in 2015 and Allianz Life in 2016.

In April, Allianz Life Insurance Korea, with assets of 16.8 trillion won, was sold to China's Anbang Insurance Group for 3.5 billion won. (Yonhap)