Miner and metals producer Alumina has reiterated its claims over its joint venture with Alcoa.
The move comes a day after the US aluminium giant Alcoa filed a plan with US regulators for the spinoff of its global upstream business.
"Alcoa's separation plan confirms our contention that Alcoa intends to exit the AWAC joint venture and transfer its interests in AWAC to a new legal entity that will not be controlled by the existing participants," Alumina chief executive Peter Wasow said.
"In our view, this is in clear breach of the AWAC joint venture agreements."
Alumina said the spin-off would trigger offer rights in its favour and require its consent.
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The company has for months sparred with its larger partner in the Alcoa World Alumina and Chemicals (AWAC) joint venture and in May the two companies took their dispute to a Delaware state court.
The dispute erupted after Alcoa in September announced it would break its global operations into two independent, publicly-traded companies - one focused on upstream mining and smelting, the other on aluminium products - in an effort to tackle the commodities slump.
Alcoa - which owns 60 per cent in the AWAC JV - has accused its Australian partner of trying to obstruct the global demerger and seeking highly valuable concessions with respect to AWAC's ownership and operation.
Earlier this week, Alumina filed a counter claim in the US court asking it to stop Alcoa's demerger from proceeding without Alumina's consent and for it be given the right to buy Alcoa's interests in the JV if it chooses.
The court has set a trial date of September 20.
