Global oil market stability is impossible without the cooperation of Russia and Saudi Arabia, the world’s biggest crude producers, the kingdom’s influential deputy crown prince said after speaking with Vladimir Putin ahead of an OPEC meeting later this month.

Saudi Arabia hopes to work with Russia for oil market stability, Mohammed bin Salman said after meeting with the Russian president in Hangzhou, China, Sunday. World leaders are gathering in China this week for a summit of Group of 20 nations. Russia and Saudi Arabia will meet with other producers in Algeria later this month to discuss oil markets.

Crude has gained about 6 percent since the Organization of Petroleum Exporting Countries said last month it will hold informal talks on oil prices and supply during a meeting of the International Energy Forum in Algiers. Producers have been discussing proposals to limit output and prop up crude after a glut cut prices by more than half from their 2014 peak.

Talks in April about a Saudi-Russian proposal to freeze output ended without an agreement in Doha, Qatar, after Iran, the group’s third-largest producer, declined to attend the meeting and Saudi Arabia balked at any accord that didn’t include all OPEC members. Putin said Thursday in an interview with Bloomberg that he’d like OPEC and Russia, producers of half of the world’s oil, to reach a deal to freeze supply and he expects the differences over Iran’s participation can be resolved.