The three competing firms are Air Liquide of France, the US-based Air Products and Germany’s Linde. Commercial bids are due by the end of June.

The estimated $100m contract covers the supply and installation of an ASU with a capacity of about 4,000 tonnes a day of oxygen.

ASUs use air feedstock to create nitrogen, hydrogen and oxygen for industrial purposes.

NIGC, established in 1983, is 70 per cent owned by Saudi Basic Industries Corporation (Sabic).