Leaders of the world's major economies are gathering in Pittsburgh today with the goal of preventing a repeat of the conditions that took them to the brink of a devastating meltdown.

President Barack Obama comes to the G-20 summit to tell world leaders that the global economy cannot continually rely on huge borrowing and spending by Americans and massive exports by countries like China.

This is the third meeting of the Group of 20 top economies in the aftermath of the financial crisis that plunged the world into fear a year ago. With the economies of the United States and many other countries under severe strain, world leaders largely agreed in April on remedies such as dramatic government stimulus.

The leaders will meet in a calmer atmosphere this time to discuss how to keep reinvigorating their economies without repeating earlier mistakes.