UN Secretary General Ban Ki-moon is due to announce details of new measures to tackle the global food crisis. The announcement is expected after a meeting of UN aid agency chiefs in the Swiss capital Berne. The UN estimates up to 100 million of the world's poorest people now need food aid due to soaring food prices. The cost of staple foods like rice, grain, oil and sugar are all at least 50% higher than they were this time last year. In the short term, the World Food Programme needs an extra $755m (£380m), as its original budget for 2008 will not be enough to cover rising prices and increased demand. But raising cash may be the easy part. Food riots have focused world attention on rising prices, and some countries, including the UK, have already promised more aid. The biggest challenge is the long term - how to promote sustainable agriculture, tackle climate change, and at the same time ensure enough food is produced. Within the UN itself opinions are divided. The UN expert on the right to food has called for the production of biofuels to be suspended, claiming they push food prices up. The head of the UN's environment programme, meanwhile, believes biofuels are key to providing alternative energy for the future. World trade talks have been stalled for years because of divisions between rich and poor countries over agricultural subsidies. Agreement might bring some stability to world food prices, but any deal is likely to be still a long way off. The increasing costs of basic foods has triggered unrest in several countries. The Haitian prime minister was forced from office earlier this month after the soaring cost of rice and beans triggered violent disturbances in the capital Port-au-Prince. A host of countries across Asia have suspended rice exports amid fears that insufficient domestic supplies could lead to acute instability. The UN's two-day meeting in Berne is being attended by the heads of 20 agencies as well as World Bank president Robert Zoellick and World Trade Organization boss Pascal Lamy (BBC)