Chinese officials have told their Iranian counterparts to intervene in the Houthi rebel group’s ongoing attacks on merchant vessels in the Red Sea—or risk losing a crucial trade partner, Reuters said on Friday, in the first known report of direct discussions about the subject.

“Basically, China says: ‘If our interests are harmed in any way, it will impact our business with Tehran. So tell the Houthis to show restraint,’” said an Iranian official briefed on the talks, according to Reuters, which said the Chinese government was now pressing the Islamic Republican to “rein in” the Yemen-based fighters.

Beijing has publicly stated that it disapproves of disruptions to international shipping and is for maritime security more generally. However, it has not openly condemned the Houthis, who have launched repeated drone and anti-ship ballistic missile strikes on commercial vessels in the Red Sea.