Grain silos in Ukraine's government-controlled territory are about half full in the run-up to this year's harvest, meaning crops could be left in the ground if Russia continues to blockade the country's ports, the head of the Ukraine Grain Association said on Wednesday.

There are some 30 million tonnes of grain stored in Ukrainian-held territory out of capacity of around 55 million tonnes, Mykola Gorbachov told an International Grains Council (IGC) conference in London, adding there were 13-15 million tonnes of storage capacity in Russian-occupied areas.

World food prices have soared to record levels and hunger levels are rising around the globe following Russia's Feb. 24 invasion of Ukraine, the world's fourth largest grains exporter.

Gorbachov said without access to its Black Sea ports, Ukraine would at best be able export 20 million tonnes of grains next year, with alternate routes via road, river and rail limiting exports to no more than 2 million tonnes a month.

That compares to shipments of 44.7 million tonnes last year.

Ukraine and the West accuse Moscow of weaponising food supplies. Russia blames the situation on what it says are Ukrainian mines in Black Sea waters and on international sanctions against Moscow.

Gorbachov estimated half of Ukraine's corn crop will be left in the ground, unharvested, if Russia maintains its blockade of the Black Sea ports. Ukraine is the world's fourth-largest corn exporter.

"I can tell you we won't find a solution (for) exports (without Black Sea port access)," he told the IGC conference.

The United Nations is trying to broker a deal to enable Ukraine's grain to be shipped from ports such as Odesa, while Turkey has also been holding talks with Russia aimed at securing Ukrainian exports via ports.

Gorbachov said the Turkey-Russia talks were not likely to lead to the security guarantees required to ship and instead called on the United States, Britain and France to provide safe convoy for vessels carrying Ukrainian grains out the country.

"I don't believe any company will load (Ukrainian) grain if the Russians sign something with the Turks. Insurance won't cover this risk. We need international guarantees, only in this case the grain will move," he said.