PSA, the world's second-biggest container terminal operator, whose global network encompasses 160 locations in 42 countries, had acquired the stake in the Hong Kong-based conglomerate's ports business for $4.4 billion in 2006.

PSA was not immediately able to provide comment to a Reuters query. Both Temasek and CK Hutchison, the conglomerate of retired billionaire Li Ka-shing, declined to comment.

PSA is in the early stages of evaluating an exit from CK Hutchison's ports business and some potential bidders have been tapped, said the sources, who did want to identified due to the sensitivity of the matter.

CK Hutchison's ports division is one of the world's largest port operators but its mainstay Hong Kong business has been facing tough competition from Chinese ports in the last few years.

Reuters was not immediately able to ascertain the estimated valuation of PSA's stake being offered for sale.

(Editing by Jacqueline Wong)

By Anshuman Daga