Kiev, March 9 : Visiting UN Secretary-General Antonio Guterres and Ukrainian President Volodymyr Zelensky have called for the extension of the Black Sea Grain Initiative, which expires on March 18. This is the UN chief's third visit to Kiev since Russia launched its ongoing full-scale invasion of Ukraine on February 24, 2022. On July 22, 2022, Russia and Ukraine separately signed a document in Istanbul with Turkey and the UN to allow Ukraine and Russia to export grain and fertilizer to ensure supplies to global markets amid the Russia-Ukraine war. The deal, due to expire on November 19, 2022, was extended for another 120 days. The UN chief has repeatedly called for the deal's further extension. In a joint press conference with the President on Wednesday, Guterres said the Black Sea Grain Initiative, agreed last July in Istanbul, has provided for the export of 23 million tonnes of grain from Ukrainian ports. "It contributed to lowering the global cost of food and has offered critical relief to people, who are also paying a high price for this war, particularly in the developing world. "Indeed, the Food and Agriculture Organization's Food Price Index has fallen by almost 20 per cent over the last year. Exports of Ukrainian -- as well as Russian -- food and fertilizers are essential to global food security and food prices. "I want to underscore the critical importance of the rollover of the Black Sea Grain Initiative on March 18 and of working to create the conditions to enable the greatest possible use of export infrastructures through the Black Sea, in line with the objectives of the initiative," he was quoted as saying. On his part, Zelenksy also stressed the importance of the initiative for global food security. "The continuation of the Black Sea Grain Initiative after March 18 is critically necessary for the whole world," he said. The Secretary-General reiterated that Russia's invasion of Ukraine is a violation of the UN Charter and international law. "The sovereignty, independence, unity and territorial integrity of Ukraine must be upheld, within its internationally recognized borders," he added. /IANS