New York, May 19 : Russia's invasion of Ukraine could soon cause a global food crisis that may last for years, the UN has warned, BBC reported. Secretary-General Antonio Guterres said the war had worsened food insecurity in poorer nations due to rising prices. Some countries could face long-term famines if Ukraine's exports are not restored to pre-war levels, he added, BBC reported. The conflict has cut-off supplies from Ukraine's ports, which once exported vast amounts of cooking oil as well as cereals such as maize and wheat. This has reduced the global supply and caused the price of alternatives to soar. Global food prices are almost 30 per cent higher than the same time last year, according to the UN. Guterres said the conflict -- combined with the effects of climate change and the pandemic -- "threatens to tip tens of millions of people over the edge into food insecurity followed by malnutrition, mass hunger and famine". "There is enough food in our world now if we act together. But unless we solve this problem today, we face the spectre of global food shortage in the coming months," he added, BBC reported. He warned that the only effective solution to the crisis was reintegrating Ukraine's food production, as well as fertiliser produced by both Russia and Belarus, back into the global market. Russia and Ukraine produce 30 per cent of the world's wheat supply and -- prior to the war -- Ukraine was seen as the world's bread basket, exporting 4.5 million tonnes of agricultural produce per month through its ports. But since Russia launched its invasion in February, exports have collapsed and prices have skyrocketed. They climbed even further after India banned wheat exports on Saturday. The UN says around 20 million tonnes of grain are currently stuck in Ukraine from the previous harvest which, if released, could ease pressure on global markets, BBC reported. /IANS