This is the latest in a series of measures taken by the aviation-to-financial services conglomerate to address a liquidity crunch, triggered by a debt-fuelled $50 billion acquisition spree over the past two years.

HNA sold an office building located in 1 York Street in Sydney to Blackstone, one source said. The group had bought the asset in 2011 for around A$117 million, the other person said.

Both sources, who did not want to be named as they were not authorized to speak to media, pegged the value of the deal at about A$200 million.

Blackstone declined to comment on news of the sale, which was first reported by Bloomberg, while an HNA spokesman said the company would address the matter in a statement soon.

Amid increased scrutiny of its opaque ownership and use of leverage, HNA has over the past few months focused on scaling-back its offshore real estate investments, which Beijing has targeted with capital controls.

Group CEO Adam Tan said in November the company would not invest in areas that were not backed by the central government.

Zhao Quan, a board director, told Reuters last month HNA would sell 1180 6th Avenue in New York and was reviewing its overseas assets. HNA's property portfolio includes buildings in New York and London.

HNA Investment Group Co announced this week that it had terminated its plan to create a real estate investment trust in Singapore.

The group has also walked away from anticipated deals, such as a bid to buy Value Partners Group, the Hong Kong-listed asset manager.

With respect to existing investments, HNA is looking to reduce exposure in some by seeking partners and selling shares.

It is in talks with a number of developers and private equity firms for co-investments in its multi-billion dollar Hong Kong development project, according to people familiar with the matter. The group did not immediately comment on the situation.

The group's borrowing, including bank loans and bonds, surged more than a third in the first 11 months of 2017 to 637.5 billion yuan ($101 billion), a China bond market filing shows.

($1 = 1.2424 Australian dollars)

($1 = 6.3180 Chinese yuan renminbi)

(Reporting by Kane Wu; Editing by Himani Sarkar)

By Kane Wu and Matthew Miller