New York: Saudi state oil giant Aramco and US firm Dow Chemical signed a deal on Saturday to build a massive chemical plant in the eastern Saudi port city of Jubail, a joint statement said.

The signing follows a late July announcement of the USD 20 billion plan that will establish the Sadara Chemical Company.

The first production units are expected to come online in the latter half of 2015, Aramco said at the time.

The site of the new company will comprise 26 plants, which will manufacture polyurethane, propylene glycol, low-density polyethylene and plastics for a range of industries.

With initial output estimated at three million tons a year, the products will be marketed directly in Saudi Arabia and seven other countries in the region.

Dow Chemical will be responsible for global sales.

Saudi Arabia, the world's biggest oil exporter, and other oil-rich Gulf states are making efforts to diversify their economies that depend heavily on revenues from crude.