Saudi Arabia's state owned oil company will begin buying liquid natural gas from a U.S. company under a 20 year agreement.

Saudi Aramco said Wednesday it would buy 5 million tons of liquid natural gas per year from Sempra Energy, based in San Diego.

Aramco will make a 25% equity investment in an LNG export facility under development in Port Arthur, Texas, as part of the deal.

Sempra CEO Jeff Martin said that the company is pleased to partner with Saudi Aramco, the largest oil and gas company in the world, to help develop the natural gas liquefaction facility in Texas.

Aramco CEO Amin Nasser says the agreement is a major step forward in the company's long-term strategy to become a global LNG player.