A deal is vital to the world's food security, ITV News correspondent Emma Murphy reports
Kremlin spokesman Dmitry Peskov on Monday said the Black Sea Grain Initiative (BSGI) would be suspended until demands to get Russian food and fertiliser to the world are met.
He added that Moscow's decision was not influenced by an earlier attack on a bridge connecting Crimea to the Russian mainland.
"When the part of the Black Sea deal related to Russia is implemented, Russia will immediately return to the implementation of the deal," Mr Peskov said.
Russia's decision marks the end of a deal which the United Nations (UN) and Turkey had brokered last summer, following the invasion of Ukraine.
Both nations are major global suppliers of wheat, barley, sunflower oil and other food that developing nations rely on.
The UK imports almost no wheat from Ukraine and supplies originate mostly from British farms.
Russia's refusal to renew the deal saw an upturn in global wheat prices on Monday, although analysts expect the rise be temporary.
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The BSGI had provided guarantees that ships would not be attacked entering and leaving Ukrainian ports, while a separate agreement facilitated the movement of Russian food and fertiliser.
Ukrainian President Volodymyr Zelenskyy has said he wants to keep the initiative going even without Russia's safety assurances for ships.
"We are not afraid," he said, adding that shipping companies had told him "everyone is ready to continue supplying grain" if Ukraine and Turkey offered support.
UK Foreign Secretary James Cleverly has accused Russian President Vladimir Putin of using food supplies "as a weapon".
He added that the decision "hurts the world's poorest".
The BSGI has allowed three Ukrainian ports to export 32.9 million metric tones of grain and other food to the world, according to the Joint Coordination Centre (JCC) in Istanbul.
Russia has repeatedly complained that the deal largely benefits richer nations.
But JCC data shows that 57% of the grain from Ukraine went to developing nations, with the top destination being China - which received nearly a quarter of the food.
UN Secretary-General Antonio Guterres said the end of the deal will result in more human suffering, but that the organisation would keep working to ensure the flow of supplies from Ukraine and Russia.
Ukraine can still export goods by land or river through Europe, but those routes have a lower capacity and have stirred divisions among its neighbours.
Since it was originally agreed, the deal has faced setbacks, with Russia pulling out briefly last November before performing a U-turn.
In both March and May, Moscow only agreed to extend the deal by a further two months instead of the usual four.
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