Secretary of State John Kerry gestures as he speaks in Washington, during the Resilience and Food Security in a Changing Climate discussion at the US Africa Summit. (AP Photo/Susan Walsh)

Washington - US Secretary of State John Kerry touted Africa's economic potential Monday as scores of African leaders arrived in Washington for the largest ever gathering of the continent hosted by a US leader.

“Africa can be the marketplace of the future,” Kerry told ministers at the World Bank on the sidelines of the US-Africa Leaders Summit.

Investment is a key component of the summit and Kerry called for more US companies to invest in Africa and urged Congress to pass an updated version of the African Growth and Opportunity Act (AGOA), which expires in 2015.

The three-day summit kicked off with a forum on civil society followed by discussions on women, health, food security and wildlife trafficking.

Vice President Joe Biden told civil society leaders they must work to root out corruption.

“It's a cancer on Africa as well as around the world,” he said. “Widespread corruption is an affront to the dignity of its people and a direct threat to each of your nation's stability.”

He pledged US support in helping the continent to address its challenges.

On Tuesday, leaders will hold a forum with top US business leaders. The summit culminates in a meeting Wednesday between the leaders and President Barack Obama to discuss investment, security and governance.

The leaders or foreign ministers of 50 African countries are attending the event.

Zimbabwe, Sudan, the Central African Republic and Eritrea were left off the guest list. Western Sahara, which is not recognized by the United States, was also not included.

Ellen Johnson Sirleaf of Liberia and Ernest Bai Koroma of Sierra Leone have said they will not attend to focus on controlling the Ebola outbreak in their respective countries.