WMC has not been impressed with Xstrata's attention

WMC Resources last month rejected Xstrata's hostile A$7.4bn ($5.8bn; �3bn) bid. The Australian firm said Xstrata's offer greatly under-valued its business.

Zurich and London-listed Xstrata is now appealing directly to WMC shareholders.

Last year, it acquired Australia's largest copper miner - MIM Holdings.

Big players

The final decision on whether to approve any acquisition rests with Australia's Treasurer Peter Costello.

WMC Resources, the world's third-largest producer of concentrated nickel, and also a miner of copper and uranium, saw its shares rise 0.3% to A$7.14 following the regulator's decision.

They hit a high of A$7.39 last month on the bid speculation.

Xstrata is a global mining giant with operations in Australia, South Africa, Spain, Germany, Argentina and the UK.

Its core products are copper, coking coal, thermal coal, ferrochrome, vanadium and zinc. It also has growing businesses in gold, lead and silver.