The firm estimated the cost of the project at $3 billion, which is 20 percent above the projected cost announced in June when the two firms unveiled the expanded petrochemicals project in the Chinese region of Tianjin, state-controlled SABIC said.
The original plan for the joint venture, released in January, had given its cost as $1.7 billion.
Construction works of the plant will be completed in September, SABIC said without specifying when production would start.
The plant's products will include ethylene, polyethylene, polypropylene, glycol-ethylene and butanediol, SABIC said noting that the plant has an annual production capacity of 3.2-million tonnes.
The two firms said in June the plant would produce 4 million tonnes of petrochemical products.
A deal for the project in north China's Tianjin was signed during Chinese Vice President Xi Jinping's visit to Saudi Arabia last year. (Reporting by Souhail Karam)