The BHP board meets in June and group president for energy, Phil Aiken, reportedly told the briefing this week that BHP's involvement in the expansion was likely to be approved at the meeting, even if the joint venture had yet to secure additional sales contracts to underpin the expansion.

BHP defended the timing of its decision saying it had rigorous internal approval process for expenditure on new investments – put in place following $10 billion in disastrous investments made in the 1990s which eventuated in nothing.

The fifth production train will virtually be a copy of the just completed fourth train, built at a cost of $2 billion, and will bring the production capacity of the NWS facility to almost 16 million tonnes per annum.