The Middle East’s biggest ever deal had been first mooted last year after the initial public offering of Aramco was postponed because investors balked at the crown prince’s $2 trillion valuation. Aramco’s purchase of the Sabic stake gets funds to the PIF by a different route.

The purchase also subtly shifts Aramco’s center of gravity away from its core business of pumping oil — about one-in-10 barrels globally — into the chemicals that are the building blocks of plastic goods. Saudi Aramco is keen to push into petrochemicals as demand growth for gasoline and other fuels starts to slow because of the global fight against climate change.

“This transaction is a major step in accelerating Saudi Aramco’s transformative downstream growth strategy of integrated refining and petrochemicals,” Amin Nasser, chief executive officer of Aramco, said in a statement on Wednesday.

The deal values the Public Investment Fund’s 70 percent stake at 123.4 riyals per share, according to the statement. The remaining shares, list on the Saudi stock market, aren’t part of the transaction and will continue trade publicly.

Aramco didn’t say how it plans to finance the acquisition, but in the past the company has said it’s likely to tap the global capital markets for the first time ever. If the Saudi state-owned company issues bonds in dollars, it will be forced to release detailed financial statements for the first time since its nationalization in the late 1970s.

Under the leadership of Yasir Othman Al-Rumayyan, the sovereign wealth fund is shifting its investment focus from domestic assets — with stakes in the likes of Sabic and National Commercial Bank — to international, funneling billions of dollars into high-profile overseas deals, including a stake in Tesla Inc. The fund lies at the heart of Saudi Arabia’s effort to reduce its reliance on oil revenue under an economic transformation plan known as Vision 2030. In addition to running the PIF, Othman Al-Rumayyan is also a director at Aramco.

Aramco plans to invest $500 billion over the next decade, and much of that will be on refineries and chemical plants. The company wants to secure future demand for its barrels, and acquiring control of the Middle East’s biggest chemical maker would bring it closer to its goal of becoming one of largest producers of raw materials used to make plastics.

Saudi Aramco may stagger payments for the Sabic acquisition, offering flexibility in how to finance the largest deal in the kingdom’s history, Energy Minister Khalid Al-Falih said in January.

The company has very little debt, but is planning to issue international bonds for the first time. Saudi Aramco picked banks including JPMorgan Chase & Co., Morgan Stanley, Citigroup Inc., HSBC Holdings Plc and National Commercial Bank to manage the bond sale, people familiar with the matter have said.