The European Commission's objections to BHP Billiton's $80bn hostile bid for Anglo-Australian mining rival Rio Tinto will spill into the public domain this month with the regulator tipped to demand the sale of iron ore assets as a prerequisite for its blessing.

BHP won't comment but observers in Australia are suggesting it may spin-off or demerge iron ore assets to create a viable new competitor and appease anti-trust concerns about the market power of a combined BHP/Rio.