Aluminum Corp. of China, the nation's largest maker of the metal, hasn't decided on whether it will increase its stake in Rio Tinto Group, Chairman Xiao Yaqing said.

    Chinalco, as the company is known as, on Aug. 24 won permission from the Australian government to raise its stake to 11 percent. It bought a 9 percent stake in London-based Rio in February with Alcoa Inc.

    A bigger stake held by Chinalco may hinder BHP Billiton Ltd.'s attempt to buy Rio Tinto for $143 billion in what would be the world's largest mining acquisition. Chinalco bought the stake to diversify into other metals, Xiao said previously.

    Chinalco's purchase of a stake in Rio was the ``right decision,'' Xiao told reporters in Shanghai today.

    Rio, which has about half of its operations in Australia, fell 1.9 percent to A$125.12 at 9:40 a.m. Hong Kong time after declining as much as 2.7 percent.

    State-owned Chinalco and U.S.-based Alcoa bought shares in Rio's London-listed stock for 6,000 pence apiece. Rio's London shares closed at 5,229 pence on Aug. 29.