June 28 (Reuters) - Hong Kong-based conglomerate Swire Pacific Ltd said on Wednesday it would sell unit Swire Coca-Cola, USA for $3.9 billion to its controlling shareholder, John Swire & Sons Ltd.

Swire Pacific expects a consolidated gain of about HK$22.80 billion ($2.91 billion) from the sale, it said. ($1 = 7.8323 Hong Kong dollars) (Reporting by Sameer Manekar in Bengaluru; Editing by Nivedita Bhattacharjee)