After years of growing increasingly reliant on cheap and abundant wheat supplies from Russia and Ukraine, the world’s grains buyers are being forced to hunt elsewhere as trade from both countries dries up.

Ukraine’s ports are closed, and while some grain is still leaving Russia for now, traders and shipping representatives said there were little or no new deals being signed because of the uncertainty around the conflict, potential new sanctions and surging costs for freight and insurance. Top importer Egypt held a wheat tender Monday but canceled it after only getting high-priced offers for French and American supplies.

It’s hard to overstate the role that Russia and Ukraine play in the global food trade. The two countries account for more than a quarter of global wheat trade, nearly a fifth of corn, and a whopping 12% of all calories traded globally, according to one estimate. Prices for both crops surged on Monday.