WRAPUP 4-Rudd presses China to release detained Australian

(For full coverage of the iron ore probe, click [ID:nSP473911]

* Rudd presses China to release Australian

* Wider probe could open rift within Chinese steel industry

* Case casts shadow on Australia-China trade worth $53 bln

By Michael Perry and Lucy Hornby

SYDNEY/BEIJING, July 14 (Reuters) - Australian Prime Minister Kevin Rudd said on Tuesday efforts to free an Australian detained in China over claims of spying took precedent over bilateral ties and he was not worried about antagonising Beijing.

Chinese investigators have questioned executives at several steel mills in a widening probe of alleged leaks of state secrets to the world's second-largest iron ore miner Anglo-Australian Rio Tinto (RIO.L)(RIO.AX), steel officials and Chinese media said.

The Shanghai State Security Bureau earlier this month detained Australian Stern Hu, Rio's iron ore salesman in Shanghai, and three of his Chinese colleagues, alleging they "pried and stole" state secrets.

"Australia's national interest always and under every circumstance comes first," Rudd told local radio. "That means the wellbeing of any Australian citizen. They come first."

Rudd said he would pursue every avenue to free Hu in a case that has cast a shadow over bilateral trade worth $53 billion last year. China is Australia's major trade partner.

The investigation has left 2009 iron ore price negotiations between China's iron and steel association and miners Rio, BHP Billiton (BLT.L)(BHP.AX) and Brazil's Vale (VALE5.SA) in limbo.

Rudd, a former Beijing diplomat and fluent Mandarin speaker, is under domestic pressure to contact Chinese President Hu Jintao to seek the Australian's release.

Rudd said he had raised the case with China's vice foreign minister in Italy last week and that Canberra was vigorously pursuing diplomatic channels.

"We will take this up at whatever level of the Chinese government is necessary as facts in each level of this complex case come clear," Rudd said. "Our interest is the individual concerned -- Mr Hu and his wellbeing. We're not interested in political grandstanding."

Asked if he was worried about antagonising Beijing, Rudd said: "Absolutely not".

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