A joint venture between Japan's Sumitomo Chemical and Saudi Aramco, the company now produces an annual 18 million tons of refined products and 2.4 million tons of petrochemicals.

A second phase of development will add 17 plants though will not expand refinery capacity.

London-based MEED magazine reported this month that the joint venture partners in the project might delay the second phase pending a new feasibility study but Saudi-based sources said they have heard of no delays.

Industry sources said Saudi-based firms had received five of seven engineering, procurement and construction (EPC) packages.

A meeting will be held in early June in Saudi Arabia to identify the scope of work and Aramco officials have said a final investment decision on the project would be taken by the end of the year.

The complex is integrated with a 400,000-barrel-per-day crude oil refinery in Rabigh on the Red Sea coast representing about 19 percent of Saudi Arabia's total refining capacity.

As part of the expansion, the firms will consider increasing the capacity of the existing ethane cracker to take in an additional 30 million cubic feet per day of feedstock ethane.

The venture will also consider building an aromatics complex using around 3 million tons per year of naphtha as feedstock. It is also looking at constructing various petrochemical units.

The cost is expected to range between $6 billion and $8 billion, Saudi Aramco Chief Executive Khalid Al-Falih said in December.

Japan's JGC Corp. is carrying out the front-end engineering and design (FEED) of the second phase of expansion.

PetroRabigh CEO Ziad Labban said in March financing will determine the equity partners of the expansion.

Bidding has already started for another petrochemical complex in Jubail, on the Gulf coast shared by Aramco and US Dow Chemical, sources said.

The second phase of PetroRabigh and the new complex with Dow are set to almost double Aramco's chemicals manufacturing capacity, Al-Falih said in April.