Vietnam has denounced China's opening of offshore oil blocks to foreign companies as "illegal" and urged international oil companies not to take part in the bidding.

Vietnam's foreign ministry says the blocks lie entirely within Vietnam's 200-mile exclusive economic zone.

Hanoi said the tender by the China National Offshore Oil Corporation "seriously violated" Vietnam's sovereignty.

The war of words again highlights regional tensions in the South China Sea, which is rich in mineral resources.

Presenter: Sen Lam

Speaker: Le Hong Hiep, international relations lecturer, Vietnam National University

LE: PetroVietnam, the Vietnamese oil company has issued a request to international oil companies not to participate in the bidding for the nine blocks offered by China. So, basically, there's been an exchange of criticisms between the two countries and it's very likely that China's decision to offer these blocks to international bidders was in retaliation for Vietnam's recent passing of a maritime law, in which Vietnam confirmed the national sovereignty of the Spratly and the Paracel islands. So, because of the timing, the Chinese authorities offered the blocks, it was just two days after Vietnam's decision to pass the law, so I think it has something to do with the Vietnamese decision to pass the maritime law.

LAM: Of course, this latest move by China comes against a background of ASEAN trying to work out a Code of Conduct in the South China Sea .. How is that coming along, this Code of Conduct document?

LE: Actually, the Code of Conduct has been a long term project for ASEAN and Vietnam. It is based on the DOC, the Declaration of Conduct of parties in the South China Sea, which was held in 2002, so ten years have passed. Recently, they agreed on the guidelines on the implementation of the DOC, but there's not been much substantial improvement at all. China is trying to buy time, and it does not want to be bound by a legally-binding document like the COC (Code of Conduct)

LAM: From where we sit, it would seem that such a document is meaningless without China being on board?

LE: You're right. If China is not party to the COC, then the COC is virtually meaningless, because the COC is what ASEAN looks to, to make sure that China's behaviour in the South China sea is not coercive or aggressive and that they can maintain peace within the region. Actually Vietnam does not have many options in dealing with China. Vietnam will have to rely on itself first.

So you can see that over the last few years, Vietnam has been stepping up its naval modernisation, so they have decided to acquire a number of military hardware and also six kilo-class submarines from Russia. So Vietnam is trying to modernise its military capability, to at least deter Chinese aggression in the South China Sea. So far, only Vietnam and the Philippines are mutually supportive, while other countries do not show a lot of interest in supporting Vietnam or the Philippines, in dealing with China.

LAM: Do you think the ASEAN countries, and particularly, Vietnam and the Philippines, might take some comfort in America's plan to focus its strategic and security energies on the region?

LE: Although China tries to prevent the US from interfering in the disputes, Vietnam and the Philippines have good reason to look for greater US engagement in the region. You can see that recently, the US Defence Secretary Leon Panetta, paid a visit to Cam Ranh Bay - it was a highly-symbolic visit, and it shows that Vietnam is trying to forge a closer relationship with the US, in order to deter any Chinese intention in pushing its claims aggressively in the South China Sea.

And you can see the Philippines also at the same time, seeking US assurance in helping the country out, in case of Chinese aggression in the South China Sea, to engage not only the US, but also other foreign powers, especially middle powers within the region, in the management of the South China Sea dispute.

You can see that Australia recently agreed to led the US troops to rotate through Darwin base. It's also a very high symbolic event. It shows that Australia might play a significant role in constraining Chinese ambitions in the region, especially in the South China Sea.