SEOUL, Feb 28 (Reuters) - The sale of Asiana Airlines' cargo business has attracted offers from four South Korean low-cost carriers, a source with knowledge of the matter said on Wednesday.

Jeju Air, Eastar Jet, Air Premia and Air Incheon all submitted non-binding bids, the source said.

Korean Air, South Korea's biggest carrier is set to purchase nearly two-thirds of Asiana for about $1.4 billion, but EU antitrust authorities have stipulated that Asiana's cargo business must be sold before they will give the deal their final approval.

Korean Air, Asiana, Air Premia and Eastar Jet declined comment.

Representatives for Jeju Air and Air Incheon could not be immediately reached for comment.

An acquisition of the cargo unit would encompass Asiana's freighter aircraft, airport slots, employees and contracts.

Thorny issues likely to arise in any deal negotiations include how much of Asiana's debt the buyer would take on, how the pricing will reflect post-pandemic drops in freight rates, and the age of Asiana's fleet, two other sources with knowledge of the matter said.

All sources were not authorised to speak to media about the deal and declined to be identified.

Analysts have said it is hard to estimate a value for the unit given the debt issue. Asiana had debt of about 12.7 trillion won ($9.5 billion) as of end-September, according to a company filing.

Asiana accounts for about a fifth of South Korea's market for overseas air cargo. With 11 cargo planes, it runs 21 routes to 25 cities in 12 countries, including the United States, Germany and Russia.

The airline sector has seen a wave of consolidation in recent months, with Lufthansa seeking a 41% stake in Italy's ITA Airways and British Airways and Iberia owner IAG's bid for the remaining 80% of Spanish carrier Air Europa it does not already own.

Korean Air has obtained a green light from competition authorities for the Asiana deal in 13 of 14 jurisdictions. It is still awaiting a U.S. decision. ($1 = 1,336.1100 won) (Reporting by Joyce Lee and Lisa Barrington; Editing by Edwina Gibbs)