HONG KONG, Dec 30 (Reuters) - Property developer Sunac China 1918.HK has so far received sufficient support from holders of seven of its 10 bonds to cut its onshore bond debt by more than half through a restructuring, a source with direct knowledge of the matter said on Monday.

The company needs approval from holders of all of its 10 onshore bonds worth 15.4 billion yuan ($2.11 billion) to implement the debt restructuring.

In addition to the first six approved earlier this month, bondholders of its largest onshore bond - with an outstanding of 2.9 billion yuan - expressed support by the extended voting deadline last Friday, the person said.

The company will extend the voting deadline for a third time for the rest of the bonds to Jan. 3, the person said.

Sunac declined to comment.

Once one of China's top developers, Sunac is the first that aims to slash its onshore bond debt through a company-led debt restructuring.

Progress by Sunac towards a landmark restructuring deal for yuan bonds could open the gates to a flurry of debt agreements next year, as the sector gives up on returning to financial health anytime soon.

($1 = 7.2991 Chinese yuan renminbi)

(Reporting by Clare Jim; Editing by Susan Fenton)

((clare.jim@thomsonreuters.com;))