President Bush has extended a law giving some African countries duty-free access to U.S. markets. Mr. Bush says freer trade promotes political stability.

Since its start four years ago, the Africa Growth and Opportunity Act has generated more than $340 million worth of U.S. investments in Africa.

By extending the agreement known as AGOA through 2015, President Bush says he hopes to build on that success.

"There is a growing consensus in both Africa and the United States that open trade and international investment are the surest and fastest ways for Africa to make progress," he said.

For too long, President Bush says too much attention has been focused on donor aid for Africa. He says there is nothing wrong with aid, reminding African ambassadors at the ceremony that his administration has increased those funding levels. But Mr. Bush says no amount of aid is ever enough to transform societies.

That, he says, comes from the economic opportunity and political stability of freer trade.

"By opening United States' markets, we make it more likely there will peace on the continent of Africa," said Mr. Bush. "AGOA nations are strengthening the rule of law. They are lowering trade barriers. They are combating corruption and eliminating child labor. They are setting an important example for the entire continent, demonstrating that governments that respect individual rights and encourage the development of their markets are more likely to grow economically and achieve political stability."

Thirty-seven Sub-Saharan African nations have qualified for the AGOA program which economists say has created more jobs in Africa while opening more markets for U.S. goods.

President Bush says free trade only works when it works both ways.

"See, when you sell goods in Africa, it means somebody is finding work here at home," he said. "Trade must work both ways. AGOA has been beneficial to the people of the continent of Africa and to the people of the United States of America."

President Bush says he is working with African leaders to break down trade barriers around the world, including ongoing talks ahead of the World Trade Organization meeting in Geneva later this month.