Shanghai | A Chinese-Australian property developer has been helping Beijing build an extradition case for an allegedly corrupt billionaire hiding out in the United States, ahead of President Xi Jinping's visit to Washington this week. 
Zheng Jiefu, who has been living in Melbourne for the past six years, told the Australian Financial Review he has been in close contact with the Communist Party's anti-corruption arm in recent months over his business dealings with Guo Wengui.
"China has been asking the US for a while to repatriate Guo and now they are elevating that request," Mr Zheng said in a phone interview. Mr Zheng's involvement in the high-profile case comes as the US has shown a willingness to co-operate with Beijing's "Operation Skynet", launched this year to bring back corruption fugitives from overseas.
On Friday, Washington sent back graft suspect Yang Jinjun, who had been living in the US for 14 years. Mr Yang was on a widely circulated list of 100 fugitives hiding overseas released in   April, which also included 10 people believed to be living in Australia.
Since Mr Xi came to power in late 2012, he has made the anti-corruption campaign, and international co-operation in this fight, one of Beijing's top foreign policy objectives.
This has put governments like the US and Australia in a difficult position due to Communist Party control of China's legal system and because some corruption crimes carry the death penalty.
Two weeks ago, Chinese officials reportedly met with FBI director James Comey and National Security Adviser Susan Rice to ask for the repatriation of Mr Guo and Ling Wancheng. Mr Ling is the brother of Ling Jihua, who is currently under investigation for corruption and was a former top political adviser to Mr Xi's predecessor, Hu Jintao.
Mr Guo was a close associate of Ma Jian, a former State Security vice minister and one of the most senior intelligence officials in China, who is also under investigation.
Mr Guo and Mr Ma have been accused of fabricating charges against business rivals including Mr Zheng in a bid to gain control of their assets. Last year, Mr Guo was ranked 74 on China's Hurun rich list with a fortune of 15.5 billion yuan ($3.4 billion).
"The investigation into Guo Wengui is almost complete," said Mr Zheng, who fled to Australia in 2008 after being targeted by Mr Ma and Mr Guo.
He has opted to provide information to the Party's Central Commission for Discipline Inspection and the Public Security Bureau from Australia rather than return to China. Mr Zheng was granted permanent residency in Australia 17 years ago and has invested around $40 million in property projects and tourism businesses.
Mr Yang's sister, Yang Xiuzhu, who topped China's most-wanted-100-fugitives list, is still in custody there. The US Immigration and Customs Enforcement said in   June she had violated the terms of the Visa Waiver Program and was "pending removal to China". Ms Yang, a former government official who is accused of embezzling 253 million yuan, has applied for political asylum, her lawyer said.
Key pointsZheng Jiefu has refused to return to China.
The US has sent graft suspect Yang Jinjun back to China.