Military delegations of Ukraine, Russia, and Turkey, along with UN officials, meet in Istanbul on Wednesday to discuss the safe shipment of grain waiting at Ukrainian ports.
Turkey seeks to broker a grain corridor from Ukraine across the Black Sea as part of a UN-backed effort to avert a global food crisis.
Turkey controls maritime traffic to and from the Black Sea through its Bosphorus Strait.
Ankara, which has good relations with both Kiev and Moscow, has been acting as a mediator between them since the outbreak of the Russian-Ukrainian conflict in late February.
Turkey has said it is ready to take on a role within an "observation mechanism" if a deal is reached.
Produced by Xinhua Global Service