Updated

Food aid for some 20 million of the world's poorest children will have to be cut even if rich nations provide emergency funds to relieve pressure from the rapidly spiraling cost of rice, wheat and other staples, the head of the World Food Program said Tuesday.

Josette Sheeran, executive director of the U.N.'s food aid organization, said projects providing meals to children in Kenya, Cambodia and to poor families in Tajikistan have already been hit.

Rising food prices, stoked by increased fuel costs, have led to the first global food crisis since World War II and sparked protests across the Caribbean, Africa and Asia.

Sheeran, in London for talks with British Prime Minister Gordon Brown, said short term donations, and new long-term strategies are needed.

"We need all the help we can get from the governments of the world who can afford to do so," she told a news conference.

Brown said rising food costs pose as great a threat to world prosperity as the global credit crunch, and are likely to reverse progress in the developing world and plunge millions into extreme poverty.

The British leader said urgent action to stimulate food production is needed, including a review of the impact of biofuels on global agriculture.

"Tackling hunger is a moral challenge to each of us and it is also a threat to the political and economic stability of nations," Brown said, in a statement released Tuesday before the meeting in London.

Unrest provoked by the food crisis has led to deaths in Cameroon and Haiti, and cost Haitian Prime Minister Jacques Edouard Alexis his job. Thousands of hungry textile workers have clashed with police in Bangladesh.

"Much of the world is waking up to the fact that food does not spontaneously appear on grocery store shelves," Sheeran told reporters.

Britain's International Development Secretary Douglas Alexander on Tuesday pledged an immediate $59.7 million (euro37.47 million) in additional funding from Britain for the U.N.'s World Program before London talks.

Brown said he fears the use of agricultural land to produce biofuels — intended to help tackle climate change — may be a key factor in driving up prices.

Many officials claim shortages are being exacerbated by poor harvests caused by unpredictable weather and because of increased demand from emerging economies like China and India.

Britain introduced targets this month aimed at producing 5 percent of transport fuel from biofuels by 2010, but Brown said Tuesday that his government will now review the policy.

Rajat Nag, head of the Asian Development Bank, said on Monday that governments across the world should question their use of agricultural subsidies to encourage biofuel production.

Production of biofuel leads to destruction of forests and reduction of the land area available to grow crops for food, Nag said. Paying farmers to grow oilseed and other crops to produce biofuels means they grow fewer food crops, resulting in higher prices for staples such corn.

Sheeran has called on 20 heads of government to offer emergency funding to help poorer countries offset the rising costs of producing, or importing, food.

She told reporters at a news conference that around US$300 million (euro188.31 million) of a required US$500 million (euro313.85 million) in short term aid has been raised.

School feeding projects in Kenya and Cambodia have already been scaled back, while the agency has cut food aid by 50 percent in Tajikistan, Sheeran said.

In the long term, developing world governments, particularly in Africa, need to dedicate at least 10 percent of their budgets to agriculture to boost global food production, Sheeran said.

World Bank head Robert Zoellick has said as many as 100 million people could be plunged deeper into poverty by the crisis. U.N. Secretary-General Ban Ki-moon said rising prices threaten to cancel out progress made toward meeting the goal of halving world poverty by 2015.