(Bloomberg) -- Rio Tinto Group and South32 Ltd. have offered Japanese clients third-quarter aluminum supply at record premiums, said traders familiar with the matter, after conflict in the Middle East tightened the global market.

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The refined metal was offered at a premium of $460 a ton by Rio Tinto, while South32 proposed $480 a ton, according to the traders, asking to not be named because the discussions are private. If accepted, that would eclipse the second-quarter supply deals with the miners by more than $100.

Rio Tinto and South32 declined to comment. Shanghai Metals Market first reported the offers this week.

The Asian nation is a major aluminum importer and the Japan premium, known as the Main Japanese Port — or MJP — is widely considered a benchmark that reflects demand in east Asia. Rio Tinto is a top supplier of the metal used in automobiles to appliances thanks to its smelters in Canada and Australia.

Aluminum futures have rallied around 17% in London since the start of the Iran war in late February, after the near-closure of the Strait of Hormuz cut off supply from a region that accounted for about 9% of global production capacity. Japan imported about a third of its aluminum from the Middle East in 2025.

The US Midwest premium — the surcharge over global benchmarks to deliver the metal into that region — has advanced to a record high on the back of the war, extending a surge after President Donald Trump hiked tariffs on the metal.

--With assistance from Winnie Zhu and Katharine Gemmell.

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