Former U.S. President Bill Clinton has rallied world leaders, celebrities and scholars to discuss ways to combat world issues such as global warming, poverty, health and education.

The Clinton Global Initiative summit, now in its third year, began Wednesday in New York.

The three-day summit will include plenary sessions during which more than 1,000 attendees from 72 countries will debate and determine the best ways to take action against pressing global problems.

Former Vice President Al Gore attended the summit to campaign for more action against global warming. Mr. Gore said there is a need for changes in laws, policies and leadership.

Thanks to previous summit's, more than 857,000 children under the age of five have received access to lifesaving medical treatment like vaccines. By the end of this year the initiative will have treated 34 million people for neglected tropical diseases.

Those who attend the summit have to pay $15,000 and those who do not make good on their commitments are not invited back the following year.

Some information for this report was provided by AFP, AP and Reuters.