LONDON (AP) — Growing global hunger because of rising food prices threatens to set back development in some of the world's poorest countries, Prime Minister Gordon Brown warned Thursday.

In a letter to world leaders ahead of a July summit of the Group of Eight industrialized nations, Brown cautioned that "rising food prices threaten to roll back progress we have made in recent years on development."

Surging food prices, combined with rising fuel costs, have triggered unrest around the world in the past month. One person was killed in two days of rioting in Egypt earlier this week, while similar clashes are wracking Haiti.

Brown's office said he sent the letter to Japanese Prime Minister Yasuo Fukuda, host of the summit, and the other G-8 leaders. He also sent it to U.N. Secretary-General Ban Ki-moon, Dominique Strauss-Kahn of the International Monetary Fund and World Bank President Robert Zoellick.

The prime minister called for the use of genetically modified crops to be reconsidered for the sake of resolving food shortages.

"We must take the initiative to further develop higher-yielding and climate resilient varieties of crop," he wrote.

Brown urged fellow leaders to provide more assistance for the very poor and to focus on infant nutrition. He also appealed for more humanitarian funding to cover the rising costs of food aid.

World Food Program executive director Josette Sheeran, who also received the letter, last month asked donor countries for $500 million to prevent cuts in its deliveries due to soaring food and fuel costs.

A letter to governments warned that the U.N. body would need to cut rations to some of the world's most impoverished regions starting next month.

British lawmakers and environmental scientists have criticized Brown's government for promoting biofuels as an alternative and less polluting fuel, saying their production leads to forests being destroyed and requires energy-intensive processing.

Some biofuels also are made from food crops, such as corn, sugar cane and wheat.