Addressing the 77th General Assembly, Duda said the international community could not "show tiredness" with the war in Ukraine, one of the global consequences of which is a food crisis and the spectre of widespread famine.
He said Russia had not limited itself to attacking the Ukrainian army, but had also killed civilians or forced them to resettle in Russia, destroying everything it could not take over or loot while also threatening the whole world with nuclear catastrophe.
"The decision to start that terrible war was taken in Russia by people motivated by imperial and colonial sentiments, by nationalistic Russian pride," Duda said, adding that Russia must lose the war.
"Moreover, the aggressor has already lost," he told the UN, "because it has not managed to tame a free country, has not broken the Ukrainian spirit, has not suppressed the Ukrainian army. Today it (Russia) has against it not only the Ukrainian state but it has against it multi-million nations, the vast majority of which do not want any negotiations today with the aggressor as long as it has not withdrawn its forces from occupied Ukrainian territory."
Duda assured the Assembly that Ukraine could count on Poland as an ally and urged the UN to also support Ukraine, which he said he was convinced would win the war and re-establish its internationally recognised borders.
The Polish president also emphasised the economic consequences of the war, in particular the food crisis it has caused, describing Russia's actions as a war against the whole of humanity.
Duda said that since the start of the war, Russia had "consciously and cynically destroyed crops and agricultural machinery," as a deliberate policy aimed at weaponising food. He said Russia had occupied 22 percent of Ukraine's arable land and had looted crops.
Pointing out that Ukraine is one of the world's most important food providers, Duda said this year's harvest would be 35 percent down, eliminating a third of the world's breadbasket. He described this as an "economic weapon" targeting the countries of Africa and the Middle East and threatening around 47 million additional people with chronic hunger. Comparing this with Stalin's notorious Ukrainian famine in the 1930's, Duda said such an artificial famine could not be allowed in the 21st century.
He added that he seriously doubted international law was sufficient to adequately punish the perpetrators of such "enormous damage to the environment and world food resources," and called on the Assembly to create more effective mechanisms to penalise those who "consciously destroy crops in the world's granary," adding that the culprits "must know that they will be sought out till the ends of their lives."
The Polish president ended by calling for tougher action against Moscow and its ally Belarus, as well as providing greater aid for the Ukrainian people.
"We cannot, the international community cannot, show tiredness with this war," Duda said. "We must support (Ukraine)." (PAP)