UN Secretary-General Antonio Guterres has revealed that one of the three Ukrainian ports covered by a UN-backed grain deal has been excluded.

Under the Black Sea grain deal, Russia and Ukraine have agreed to allow grain shipments from the ports to secure global food supply after the Russian invasion of Ukraine.

In a statement on Tuesday, Guterres expressed disappointment over the exclusion of the Pivdennyi port and raised concerns about a drop in food supply to global markets.

He called on related parties to do their utmost to ensure the continuation of the agreement, which needs to be renewed in July.

Russian Deputy Foreign Minister Sergey Vershinin told reporters on Tuesday that the United Nations is not helpful enough for Russian exports of its agricultural products. He said Russia may not extend the grain deal after it expires in mid-July.

Russian President Vladimir Putin had suggested last week that Russia would consider withdrawing from the deal. The Kremlin has expressed dissatisfaction with stalled exports of Russian products due to Western sanctions.