Saudi Aramco and US firm ConocoPhillips have extended by almost one month the deadline for bids for a solids handling unit at their joint 400,000 barrels per day (bpd) Yanbu refinery, industry sources said on Saturday.

The deadline is now due by March 22, two sources close to the bidding process said. The bids were originally due by February 28.

US firm KBR completed the front-end engineering and design (FEED) of the refinery and split the tender process into 11 engineering, procurement and construction (EPC) packages.

Saudi-based contractors submitted their proposals for five other EPC contracts that include a coking unit, a crude facility, a gasoline unit, a hydrocracker and a tank farm.

Aramco and Conoco are expected to award all contracts in May. Italy's Saipem , Argentina's Techint, UK's Petrofac, South Africa's Senet, ThyssenKrupp Robins, Flsmidth and South Korea's Daelim Industrial Company are bidding for the solids handling unit package, sources said.

Aramco is investing in refining despite very poor profitability, Aramco's chief executive Khalid al-Falih said on Thursday at the World Economic Forum.

The kingdom plans to double total domestic and international refining capacity by 2015.-Reuters