Rio Tinto has been made aware of a trial date for four of its workers in China.

The four have been charged with bribery and violating commercial secrets and will face a closed court in Shanghai on 22nd March.

Australian citizen Stern Hu, Rio Tinto's lead iron ore negotiator in China, is one of the four facing trial. He has been in detention since July last year, as have his Chinese colleagues Liu Caikui, Ge Minqiang and Wang Yon.

They could face up to 27 years in prison if Chinese prosecutors are able to prove the men exploited their positions by seeking or illegally accepting massive bribes from a number of Chinese steel firms.

The case has created a political and diplomatic problem for Australia, with China being its largest trading partner.