Ukraine and Russia are both among the world's biggest exporters of grain and other foodstuffs.
If Ukrainian grain is again blocked from the market, prices could soar around the world, hitting the poorest countries hardest.
Russia says it could return to the grain deal, but only if its demands are met for rules to be eased for its own exports of food and fertiliser.
Ukraine's President Volodymyr Zelenskiy has called for the grain deal to continue without Russia, effectively seeking Turkey's backing to negate the Russian blockade.
Any attempt to reopen Ukrainian grain shipments without Russia's participation would depend on insurance companies agreeing to provide coverage.
Persons:
Andriy Yermak, Antonio Guterres, Moscow, Dmitry Peskov, Volodymyr Zelenskiy, Tayyip Erdogan, Ukraine's counterassault, Hanna Maliar, Serhiy Cherevatyi, Peter Graff, Angus MacSwan, Alex Richardson
Organizations:
UN, United Nations, Local, Kyiv, Russian Federation, Reuters, Thomson
Locations:
Russia, Moscow, KYIV, Ukrainian, Odesa, Ukraine, Crimean, Mykolaiv, Crimea, Russia's, Kupiansk, Kyiv, Bakhmut, Turkey, Russian, Kharkiv