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GENEVA, April 18 (Reuters) - The rising cost of providing food aid will top the agenda when U.N. Secretary-General Ban Ki-moon meets heads of U.N. agencies, the World Bank and IMF in Switzerland later this month, a spokeswoman said on Friday.

Ban will host a semi-annual meeting of U.N. agency heads in the Swiss capital of Berne on April 28-29, U.N. spokeswoman Marie Heuze said.

World Bank President Robert Zoellick and IMF Managing Director Dominique Strauss-Kahn are also to attend, she said.

"The main subjects on the agenda will be the food crisis and climate change. They will look at means of coordination," Heuze told Reuters.

The World Bank has warned that higher food and energy costs, along with poor infrastructure and falling aid levels, threaten to undo several years of growth in Sub-Saharan Africa.

High prices, driven by bad harvests and record fuel costs, have triggered riots and violence in poor and developing countries including Haiti and Indonesia, especially those which rely on imports for the bulk of food supplies.

Josette Sheeran, who heads the U.N.'s World Food Programme (WFP), and Jacques Diouf, director-general of the Food and Agriculture Organisation (FAO), will be among the participants at the closed-door talks in Berne.

The WFP's initial appeal to donor countries for this year was $2.9 billion.

But due to rising food and fuel costs, the Rome-based agency issued an emergency appeal in late February for an extra $500 million to help feed 73 million hungry people in 80 countries.

Since then, the price it pays to buy Thai rice, a staple in many poor countries, has jumped from $460 a tonne in early March to $780 a tonne now. As a result, its emergency appeal has risen to $756 million, a WFP spokeswoman said.

"I can't guarantee this figure won't change again because if prices continue to rise, we'll need to act accordingly," spokeswoman Christiane Berthiaume told a news briefing.

The agency has received $900 million in donations so far, which represents only 20 percent of its overall needs of at least $3.65 billion for the year, she added.

The FAO warned last week that food riots in developing countries will spread unless world leaders take major steps to reduce prices for the poor.

Despite a forecast 2.6 percent hike in global cereal output this year, record prices are unlikely to fall, forcing poorer countries' food import bills up 56 percent and hungry people on to the streets, Diouf said at the time. (Reporting by Stephanie Nebehay; Editing by Jonathan Lynn)

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