Leaders of Ukraine and Bulgaria have discussed their countries’ cooperation on the Black Sea to secure a "grain corridor" in the wake of Russia's withdrawal from a crucial deal that has led to growing fears about global food security.

The withdrawal of Russia from the grain deal negotiated by Turkey and the United Nations has had a chilling effect on merchant shipping using the three Ukrainian Black Sea ports from which most grain is exported. Russia has warned that ships leaving these ports may come under attack.

Ukraine has since created its own maritime corridor for shipping, but it is unable to guarantee its safety because of Russian naval superiority in the Black Sea.

Ukraine’s President Volodymyr Zelensky met with Bulgaria’s Prime Minister Nikolai Denkov to talk about the corridor on the sidelines of Ukraine-Balkans Summit held in Athens, Greece on Monday.

The two leaders “discussed cooperation between the Black Sea states to ensure sustainable security in the Black Sea and the functioning of the "grain corridor" in alternative ways,” Zelensky’s office said.

Zelensky thanked Denkov for the recent Bulgarian decision to provide defense support to Ukraine, according to the office.

Some context: Kyiv is in talks with some of the world’s biggest insurance companies to cover ships traveling to and from its ports in the Black Sea — a crucial step toward a full resumption of vital grain exports around the globe.

Work on an insurance mechanism follows Russia’s withdrawal from the Black Sea Grain Initiative last month, which threatens the safe passage of ships carrying grain to and from Ukrainian ports.

The collapse of the deal — brokered by Turkey and the United Nations a year ago — has already pushed up global food prices and could tip millions in poor countries into hunger.

To keep grain shipments moving, Ukraine’s government will share potential losses with insurers, which should make cover for travel through risky Ukrainian waters more affordable for commercial shipping companies.