The Aluminum Corporation of China, or Chinalco, also issued a statement saying the case was unrelated to its failed bid to double its stake in Rio Tinto.

Chinalco was upset at Rio Tinto knocking back its bid last month to up its stake to 18 percent. Rio instead opted to splice its iron ore operations in Western Australia with those of archrival BHP Billiton Ltd.

Chinalco's $19.5-billion pitch for a bigger bit of Rio represented the biggest foreign investment bid China had ever proposed.

China alleged the Rio-BHP joint venture would concentrate too much market power because it would exert a 'monopolistic tint' to the iron ore market.

The prices of iron ore export contracts are set annually, and China is under pressure to accept the same quantum as Japan and South Korea. China had argued for a 60-percent cut on last year's fix -- not the 37-percent discount that other customers have agreed upon.