DUBAI, Nov 2 (Reuters) - Saudi Basic Industries Corp (SABIC), one of the world's biggest petrochemical companies, on Thursday posted an almost 17% dip in third-quarter revenues that swung its earnings into a net loss.

SABIC reported a net loss of 2.88 billion riyals ($767.80 million) in the three months to Sept. 30, compared with a profit of 1.84 billion riyals in the year ago period, it said in a filing.

The loss was mainly driven by the fair valuation of Saudi Iron and Steel Company (Hadeed) amounting to 2.93 billion riyals ($781.13 million), after Saudi Arabia's sovereign wealth fund acquired SABIC's entire stake in the company.

SABIC's divestment in Hadeed was agreed to in September, allowing the Saudi petrochemicals giant to "optimize its strategic portfolio and focus on its core business," it said.

($1 = 3.7510 riyals) (Reporting by Hadeel Al Sayegh; Editing by Mrigank Dhaniwala)