BG agreed to sell its 16.67% interest in two equal parts to both of the Chinese government-controlled companies, the country's second and third largest oil interests. However, the deals are conditional on BG's co-partners waiving pre-emption rights to buy the stakes for $US615 million each.

So far most partners have waived the rights leaving only Shell and Exxon Mobil undecided.

Both sides are playing down any impact the decision could have for Shell although sources have said that it could exclude the Anglo-Dutch oil group from the lucrative Chinese oil market if it decides to go ahead with the move.

The sale to the two companies would boost the prospects of a West-East pipeline from Kazakhstan to China, curbing Beijing's dependence on Middle East oil.

Letting the Chinese have direct access to energy supplies, instead of in the role of customer, goes against Shell's aim of achieving command of the global LNG and gas markets.