Stability in Saudi Arabia is the cornerstone of prosperity and progress in the Gulf, and China firmly supports Riyadh in its drive for economic diversification and social reform, President Xi Jinping told Saudi Crown Prince Mohammed bin Salman, Reuters reports.

Meeting in Buenos Aires, host of the G20 summit of industrialized nations on Friday, Xi said China has always attached great importance to its relations with Saudi Arabia, China’s official Xinhua news agency reported.

“China firmly supports Saudi Arabia in its drive for economic diversification and social reform, and will continue to stick together with Saudi Arabia on issues involving their core interests,” Xinhua cited Xi as saying.

The Saudi press agency reported early on Saturday that the crown prince and Xi discussed partnership between the two countries and harmonizing Saudi Arabia’s 2030 vision with China’s Belt and Road Initiative, as well as Saudi energy supplies to China and mutual investment.

China and Saudi Arabia have close energy ties.

Saudi Arabia is set to expand its market share in China this year for the first time since 2012, with demand stirred up by new Chinese refiners pushing the kingdom back into contention with Russia as top supplier to the world’s largest oil buyer.

Saudi Arabia, the biggest global oil exporter, has been surpassed by Russia as top crude supplier to China the past two years as private “teapot” refiners and a new pipeline drove up demand for Russian oil.

China also has good relations with Saudi’s regional rival, Iran, and has long had to balance its ties between Riyadh and Tehran.