The conference gathered more than 1,000 guests, including some 30 incumbent heads of state or government, senior international officials such as UN Secretary-General Kofi Annan and EU High Representative for the Common Foreign and Security Policy Javier Solana, business people such as Bill Gates and Warren Buffet, and numerous officials from the Clinton administration, Clinton's supporters and friends.
Before the conference, President Mesic had a 15-minute meeting behind closed doors with Clinton, former US Secretary of State Madeleine Albright, and former national security advisor Sandy Berger.
Opening the conference, Clinton thanked the sponsors, particularly the Gates family, saying that the first conference, held in 2005, had raised USD2.5 billion for different projects, and that he hoped this year's event would help raise even more money because the number of participants was three times higher.
Clinton warned that the world today was faced with an increasing number of racial and ethnic conflicts, including genocide in Darfur, renewed conflicts in Sri Lanka, and the situation in the Middle East.
The conference was first addressed by the First Lady Laura Bush, whose participation in the event many found surprising.
She stressed that since 2001, when the first term of her husband George Bush started, the United States had doubled assistance to poor countries and tripled assistance to Africa.
She also announced the launching of the Clear Water programme to provide drinking water for schools in Africa, and a programme of assistance in the treatment of HIV positive women in Africa.
The conference was also addressed by Pakistan's President Pervaz Musharraf, his Columbian counterpart Alvaro Uribe, and the first woman president of an African country, Ellen Johnson Sirleaf of Liberia.
The three-day meeting, which is being held in the Sheraton Hudson Hotel, will continue with sessions on individual areas in concern.
Also on Wednesday, President Mesic was due to attend a conference of Initiative 11 of King Abdullah II of Jordan, which is aimed at the economic development of the Middle East countries, while Croatian Prime Minister Ivo Sanader was due to address the 61st session of the UN General Assembly on Wednesday evening local time.