Ukraine’s typical harvest output could be halved this year by the Russian invasion, Ukrainian President Volodymyr Zelensky said Sunday.

“Ukrainian harvest this year is under the threat to be twice less,” Zelensky wrote in a Tweet in English.

“Our main goal — to prevent global food crisis caused by Russian invasion,” Zelensky wrote Sunday. “Still grains find a way to be delivered alternatively.”

A top global food supplier, Ukraine’s production has been disrupted by war with Russia.  The conflict has exacerbated the global food crisis, according to the World Bank, as countries scramble to navigate surging prices with trade restrictions. It’s also blocked critical ports in the Black Sea.

In 2020, Ukraine was the world’s fifth-largest supplier of wheat, and Zelensky has long been warning of global famine if the country isn’t able to export its product.

The warring countries signed an agreement last week with Turkey and the United Nations to facilitate Ukrainian grain export via the Black Sea, but dangerous waters are making shippers wary of the risks.

Zelensky visited a Black Sea port Friday to mark the first ship loaded for export since the start of the warfare.

On Saturday, Zelensky urged civilians in the easternmost Donbas region of the country to leave amid intense fighting with Russian forces.

Zelensky said in a statement that hundreds of thousands of people remain in the area and refuse to leave but must for their own safety, adding that his government is organizing for a mandatory evacuation.

Zelensky also called on the U.S. and other nations to recognize Russia as a terrorist state, saying the gesture would be an “effective defense of the free world.”