U.S. President Barack Obama delivers a speech during a symposium on Global Agriculture and Food Security in Washington D.C., capital of the United States, May 18, 2012, on the sidelines of the G8 summit. [Xinhua phtoto]

U.S. President Barack Obama delivers a speech during a symposium on Global Agriculture and Food Security in Washington D.C., capital of the United States, May 18, 2012, on the sidelines of the G8 summit. [Xinhua]

U.S. President Barack Obama delivers a speech during a symposium on Global Agriculture and Food Security in Washington D.C., capital of the United States, May 18, 2012, on the sidelines of the G8 summit.

Benin President Boni Yayi addresses the symposium on Global Agriculture and Food Security in Washington D.C., capital of the United States, May 18, 2012, on the sidelines of the G8 summit. [Xinhua photo]

Bono, the lead singer of the rock band U2 and co-founder of ONE, an advocacy organization dedicated to fighting extreme poverty and preventable disease, particularly in Africa, addresses the symposium on Global Agriculture and Food Security in Washington D.C., capital of the United States, May 18, 2012, on the sidelines of the G8 summit. [Xinhua photo]

Ghana's President John Evans Atta Mills is seen during a symposium on Global Agriculture and Food Security in Washington D.C., capital of the United States, May 18, 2012, on the sidelines of the G8 summit. [Xinhua photo] 

Tanzanian President Jakaya Kikwete speaks during a symposium on Global Agriculture and Food Security in Washington D.C., capital of the United States, May 18, 2012, on the sideline of the G8 summit. [Xinhua photo]

Ethiopian Prime Minister Meles Zenawi speaks during a symposium on Global Agriculture and Food Security in Washington D.C., capital of the United States, May 18, 2012, on the sidelines of the G8 summit. [Xinhua photo]