Backgrounder: Past Summits of the Americas

The seventh Summit of the Americas will be held here on Friday and Saturday, gathering more than 30 heads of state and government of the Western Hemisphere, including the U.S. President Barack Obama and Cuban leader Raul Castro.

This would mark a historic encounter of the two countries' leaders in half a century, as the two sides have been moving toward normalizing ties in recent months. It would also be the first time Cuba has ever attended the summit since it was launched in 1994.

Chilean President Michelle Bachelet will miss the event due to the flood crisis at home.

The summit has been held every three or four years since 1994 to foster high-level talks on regional issues and collectively address main challenges in the bloc.

The summit is sponsored by the Organization of American States (OAS), which expelled Cuba in 1962 at the initiative of the United States. The latter severed its diplomatic relationship with Cuba in 1961, shortly after then Cuban leader Fidel Castro launched a revolution that toppled a U.S.-friendly government.

The dominant presence of the United States has been a stumbling block to achieving consensus among the 34 countries, though that appeared to change dramatically in 2012, during the sixth summit held in Cartagena, Colombia.

Tired of Washington's half century grievance against Cuba, Latin American nations demanded at the summit that the Caribbean nation be allowed to join the gathering.

The OAS had also invited Cuba to rejoin in 2009, but the country declined to return to the pan-American bloc then.

Brief introductions of the previous six summits are as follows.

The first summit was held in Miami, the United States, in 1994, and helped forge a renewed commitment and partnership based on democracy, economic integration, and sustainable development.

The second summit took place in Santiago, Chile, in 1998 and focused on education, emphasizing its central importance in improving social justice, economic integration, and political dialogue.

The third summit in Quebec City, Canada, in 2001 focused on democracy and human rights initiatives as a means of creating prosperity, and stressed the role of technology.

The fourth summit took place in Mar del Plata, Argentina, in 2005 and promoted increased job creation to fight poverty and strengthen democratic governance.

The fifth summit, held in the Caribbean island nation of Trinidad and Tobago in 2009, focused on securing the future of the citizens of American countries by promoting human prosperity, energy security and environmental sustainability.

The sixth summit in Cartagena, Colombia, in 2012, focused on drug problems and women's entrepreneurship in the Americas, but it ended without a declaration because the United States' shutting out of Cuba caused boycotts from several Latin American countries. Endi