Shipments across the Black Sea have been blocked both by Russian warships and mines Kyiv has laid to avert a feared amphibious assault. The stakes could not be higher for tens of millions of people facing the threat of starvation in African and other poor nations because of the battles engulfing one of the world's main grain-producing regions
Russia and Ukraine on Wednesday made substantive progress in their first direct talks since March on a deal to relieve a global food crisis caused by blocked Black Sea grain exports.
The high-stakes meeting involving UN and Turkish officials in Istanbul broke up after slightly more than three hours with an agreement to meet again in Turkey next week.
Ukraine is a vital exporter of wheat and grains such as barley and maize, and has supplied nearly half of all the sunflower oil traded on global markets, but shipments have been disrupted since Russia invaded its neighbour in February.
UN Secretary-General Antonio Guterres said the talks had provided a "ray of hope to ease human suffering and alleviate hunger around the world" but cautioned that while he was optimistic, a deal was "not yet fully done".