ISTANBUL (AP) — Military officials from Russia and Ukraine were set to hold their governments' first face-to-face talks in months Wednesday during a session in Istanbul devoted to a United Nations plan to export blocked Ukrainian grain to world markets through the Black Sea.

Turkish military officials and U.N. representatives also planned to participate in the discussion focused on finding a way to get millions of tons of grain sitting in silos amid the war in Ukraine shipped out of the country's ports toward the Mediterranean.

Ukraine is one of the world's largest exporters of wheat, corn and sunflower oil, but Russia's invasion and war disrupted production and halted shipments, endangering food supplies in many developing countries, especially in Africa, and contributing to higher prices.

Turkey has offered to provide safe Black Sea corridors and worked with the U.N., Russia and Ukraine to reach an agreement. The U.N. would establish a center in Istanbul to control the shipments, Turkish officials have said.

Russian and Ukrainian officials have traded accusations over the stuck grain shipments, Moscow has said Ukraine's heavily mined ports are causing the delay. Russian President Vladimir Putin has pledged that Moscow wouldn't use the corridors to launch an attack, if the sea mines were removed.

Ukrainian officials have blamed a Russian naval blockade for holding up exports and causing a global food crisis. They remained skeptical of Putin's pledge not to take advantage of cleared Black Sea corridors to mount an attack, noting that he insisted at the beginning of the year he had no plans to invade Ukraine.

Ahead of the talks in Istanbul, a senior Russian diplomat said Moscow was willing to ensure safe navigation for ships to carry grain from Ukrainian ports but would press for its right to check the vessels for weapons.

Pyotr Ilyichev, the head of the Russian Foreign Ministry's department for ties with international organizations, said Russia's military had repeatedly declared its willingness to allow for safe shipping corridors in the Black Sea.

Seventy vessels from 16 countries have remained stuck in Ukrainian ports, Ilyichev said, alleging that Ukrainian authorities had barred them from departing.

"Our conditions are clear: We need to have a possibility to control and check the ships to prevent any attempts to smuggle weapons in, and Kyiv must refrain from any provocations," Russia's Interfax news agency quoted Ilyichev as saying.

U.N. Secretary-General Antonio Guterres has worked for months to secure a deal that would allow Ukraine to export wheat and other commodities from Odesa, the country's largest port, and also enable Russia to export grain and fertilizer to global markets.

Asked about Wednesday's talks, Guterres said Tuesday: "We are working hard, indeed, but there is still a way to go."

The war has trapped about 22 million tons of grain inside Ukraine, according to Ukrainian President Volodymyr Zelenskyy. U.N., Turkish and other officials are scrambling for a solution that would empty the silos in time for upcoming harvest in Ukraine.

The U.N. Food and Agriculture Organization says the war is endangering food supplies for many developing nations and could worsen hunger for up to 181 million people.

Some grain is being transported through Europe by rail, road and river, but the amount is small compared with sea routes.

Russia isn't able to transport its grain either. Moscow argues that Western sanctions on its banking and shipping industries make it impossible for Russia to export food and fertilizer and are scaring off foreign shipping companies from carrying it.

Complicating the negotiations are accusations that Russia is shipping grain that was stolen from Ukraine.

Ukraine's Foreign Ministry summoned the Turkish ambassador last week after Turkish authorities briefly detained a Russian ship suspected of transporting stolen grain but allowed it to leave and return to a Russian port. A Turkish official said authorities were not able to determine the ship carried stolen grain.

NATO-member Turkey has retained its close ties to both Moscow and Ukraine. Since the war started, it has hosted a meeting between the Russian and Ukrainian foreign ministers, as well as talks between the two countries' negotiating teams.

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Fraser reported from Ankara, Turkey.

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Follow AP's coverage of the Russia-Ukraine war at https://apnews.com/hub/russia-ukraine