Agreements on the power, water and petrochemical components of the deal have been made with the Saudi government but the deal now hinges on technical issues relating to the quantity of gas on offer.

The companies insist they should be given part of the areas reserved for Saudi Aramco, the giant national oil company, to minimise the risks, but the government has rejected this demand.

Saudi Oil Minister Ali al-Nuaimi is expected to make the ministry's final decision on the companies' proposal by mid-June.

Saudi Arabia signed preliminary agreements in June 2001 with eight international oil companies for the development of three gas projects, requiring investments of $US25 billion. The projects involve upstream, midstream and downstream facilities including the construction of petrochemical plants, water desalination, power generation, transmission and others.

If the deal folds a major restructuring of the projects could see national energy giants Saudi Aramco and Saudi Basic Industries Corp move in.

ExxonMobil won the lion's share in the initial signing, taking the lead of two consortia tasked with developing the South Ghawar field, requiring a $US15-billion investment, and the Red Sea field, needing five billion dollars which has been shelved for reassessment.

Royal Dutch/Shell was selected to lead a consortium to develop the Shaybah field in the Empty Quarter, expected to require initial investment of five billion dollars. BP Amoco and Phillips Petroleum were chosen in the South Ghawar group, and TotalFinaElf and Conoco in the Shaybah group.

Saudi Arabia, which sits atop the world's biggest oil reserves, has proven natural gas reserves of 224 trillion cubic feet (6.6 trillion cubic metres).