South Korea's STX Offshore & Shipbuilding submitted a proposal to a court on how to revive its business, a spokesman said on Saturday, as the troubled firm seeks court-led debt restructuring.

STX -- once the country's number four shipbuilder -- filed for the restructuring in May after struggling for years with mounting losses caused by mismanagement and a slump in global demand.

The court, after reviewing the firm's revival plan, is set to decide later this year whether to put it under a debt restructuring and recovery programme, or declare it bankrupt.

"The survival plan was submitted to the Seoul Central District Court on Friday," company spokesman Kong Doo-Pyoung told AFP, adding it includes a plan to sell the firm's French unit by the end of this year.

STX in 2008 bought a 67 percent stake in the huge shipyard in the western French port of Saint-Nazaire, later named STX France. It produces ships ranging from cruise vessels to warships.

The firm plans to accept bids for the French unit in October before selecting a preferred bidder in November.

STX -- part of the STX Group that has businesses ranging from shipping to construction -- has been cutting hundreds of jobs at home and selling assets to shore up its finances and avoid bankruptcy.

Creditor banks since 2013 have stumped up more than four trillion won ($2.4 billion) to help STX repay debts but failed to turn it around. 

The firm's total debts amounted to 7.3 trillion won as of June. 

South Korean shipbuilders including STX and Daewoo Shipbuilding and Marine have struggled with mounting losses as global trade slows and competition from Chinese rivals intensifies.