Bidding process for the nine oil and gas offshore blocs in the South China Sea has gone smoothly, Wang Yilin, president of state-owned China National Offshore Oil Corporation (CNOOC), told the Beijing News in an interview published Thursday.

CNOOC put up nine offshore oil blocs in the South China Sea for bidding last month, sparking protests in Vietnam.

Wang said in the interview that several U.S. firms have expressed their interest in the bidding, dismissing rumors that only oil companies in Malaysia and Thailand have taken interest because big global companies don't want to get involved in the 'mess' due to potential risks of investment return amid territorial disputes.

Another source revealed earlier to the Beijing News that CNOOC will invest 200 billion yuan ($US31.4 billion) in the next 20 years to explore oil and natural gas resources in the South China Sea and build it into a new Daqing, a northeastern Chinese city known for its oil industry boom in 1960s.

When asked to confirm, Wang said this is just a strategic plan and there is a still long way to go to turn it into reality.

A couple of days ago, Vietnam decided to extend the contract for exploration in bloc 128 in South China Sea to India's state-owned ONGC Videsh Ltd (OVL), attempting to hold on to Indian presence in the resource-rich region. OVL agreed to the contract extension, India media reported yesterday.

Wang added that China's bidding for nine oil blocs is a normal business activity of a sovereign state, and that protests in Hanoi posed no surprise at all since they had predicted strong reactions from the Vietnamese side.