Scientists from China and Sierra Leone have been named co-winners of this year's World Food Prize for pioneering work on hybrid rice varieties. The awards were announced Monday at a ceremony at the U.S. State Department led by Secretary of State Colin Powell.

The co-winners, China's Yuan Longping and Monty Jones of Sierra Leone, worked on separate but complementary research projects that produced new strains of hybrid rice that have improved crop yields in developing countries.

Professor Yuan, director of China's National Hybrid Rice Research and Development Center in Hunan, was cited for what was termed his "breakthrough achievement" for hybrid rice-breeding in the 1970s that led to the world's first widely grown varieties.

Sierra Leone's Dr. Jones, now the executive secretary of the Forum for Agricultural Research in Africa in Accra, Ghana, was honored for developing the so-called "New Rice for Africa", a cross between Asian and African strains that is both pest-resistant and able to withstand drought conditions.

The two scientists will divide a $250,000 cash award that will be formally presented to them in ceremonies in October in Des Moines, Iowa.

Announcement of the prize, given annually since 1987 by the World Food Prize Foundation, came at a State Department gathering of diplomats, leaders of non-governmental aid organizations and government officials, including Secretary of State Colin Powell.

Mr. Powell told the audience that because of advances such as those by Dr. Jones and Professor Yuan, famine in the 21st century is "entirely preventable" yet it still stalks millions of people, especially in the Horn of Africa.

He said the Bush administration is "strongly committed" to continuing America's status as the world's leading supplier of emergency food aid and has actively embraced the 1996 World Food Summit goal of reducing by half the number of chronically hungry people in the world by 2015.

The secretary of state said progress toward the goal is lagging but he said with tenacity and technology, the promotion of good governance and growth-oriented aid programs, the struggle against hunger can be won. "In the 21st century, no man, woman or child should know the agony of hunger. By recognizing the successes of those on the front lines of the fight against hunger, as we do today, we reinforce the message that the fight against hunger is a fight the world can win. And win we will, and win we must," he said.

The World Food Prizes are funded by American philanthropist and businessman John Ruan, with winners chosen by a panel headed by American scientist and Nobel Peace Laureate Norman Borlaug.

Dr. Borlaug, considered the father of the "Green Revolution" for his work in the 1960s on high-yield wheat, attended Monday's event, which came on his 90th birthday.