GENEVA (AP) — Ukraine is filing a complaint at the World Trade Organization against Hungary, Poland and Slovakia after they banned grain and other food products coming from the war-torn country, Ukrainian Prime Minister Denys Shmyhal said Tuesday.

It lays bare a widening rift with the three members of the European Union, which has been a pivotal backer of Kyiv as it works to fight off Russia’s invasion.

In a break with the wider EU, Poland, Hungary and Slovakia have announced bans on grain and other food from Ukraine, a major agricultural supplier to parts of the world where people are going hungry. The 27-nation bloc last week lifted restrictions on Ukraine’s exports to five member states, also including Romania and Bulgaria.

Farmers in eastern Europe have railed against the imports from Ukraine, saying grain has gotten stuck inside their borders and driven down prices for local growers. Farmers in Bulgaria protested Monday after their government cited higher food costs in lifting the ban on Ukrainian products.

The WTO confirmed that it received a Ukrainian request for talks with Hungary, Poland and Slovakia over the dispute, a first step toward a possible showdown through the Geneva-based trade body.

Shmyhal blasted the “unfriendly” actions by the three countries and announced an investigation of possible discriminatory practices.

But the Ukrainian prime minister also floated a possible “compromise scenario” that would control four groups of exported farm products, aiming to limit market distortion in nearby countries. The EU ban had applied to wheat, corn, rapeseed and sunflower seeds.

Shmyhal warned that Ukraine could institute a retaliatory ban on some types of goods from Hungary, Poland and Slovakia if they refused to lift their restrictions.

“Such a blockade will only benefit the Russian plan to create a worldwide food crisis,” Shmyhal said.

In July, Russia pulled out of a U.N.-brokered deal allowing Ukraine to ship grain safely through the Black Sea. Routes through Europe have become the primary way for Ukraine to export wheat, barley, corn, vegetable oil and more to developing nations in need.

Ukraine in recent days has been pushing ahead with limited exports through its own maritime channel despite the risks. Infrastructure Minister Oleksandr Kubrakov wrote Tuesday on Facebook that a vessel carrying 3,000 tons of Ukrainian grain left the port of Chornomorsk on its way across the Black Sea.

The ship was one of two to enter Chornomorsk through a corridor for civilian vessels set up by the Ukrainian Navy, he wrote.

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Novikov reported from Kyiv, Ukraine.