(Bloomberg) -- Japanese trading house Mitsui & Co. will buy a stake in an iron ore project in Australia for about $5.3 billion.

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The company will purchase a 40% holding in the Rhodes Ridge site in Western Australia, the company said in a statement. Mitsui is buying a 25% interest from VOC Group and 15% from AMB Holdings. 

The project, in the metals-rich Pilbarra region, is one of the world’s largest undeveloped iron ore deposits, with a mineral resource estimated at 6.8 billion tons. The Japanese company will form a joint venture with mining major Rio Tinto Group, which invested $77 million in development studies in 2023, to mine the site.

The deal comes as Rio struggles to maintain production of superior quality iron ore grades in the Pilbara. Rhodes Ridge is a higher-grade deposit and may help offset declines elsewhere. 

Iron ore prices have been under pressure since the start of 2024 due to China’s economic slowdown and property-market crisis. 

Mitsui shares fell as much as 3.4% in Tokyo, while Rio Tinto was up more than 1% in Sydney.

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