Leaders of the Andean Community of Nations have begun a summit meeting in Colombia which could lead to the merging of Latin America's economic blocs.
Hugo Chavez (right) says there are many obstacles to unity
The meeting near the town of Rio Negro - held amid tight security - is being attended by the presidents of Colombia, Bolivia, Ecuador and Venezuela, and the vice-president of Peru.
The Brazilian President, Luiz Inacio Lula da Silva, has been invited to join the summit, as a representative of the South American trade bloc, Mercosur.
There is talk of a possible merger between the two groupings, as Latin America tries to establish a united front for free trade negotiations with the United States.
Brazil is Mercosur's chief member, followed by Argentina and the smaller economies of Uruguay and Paraguay, while Chile and Bolivia are associate members.
The Secretary General of the Andean Community, Guillermo Fernandez de Soto, told the Latin American leaders: "Together we are stronger than apart".
"The problems in your nations cannot be resolved within national borders."
He urged the presidents to iron out their disagreements and build "a common market that will make us greater and less vulnerable to international volatility."
Venezuelan President Hugo Chavez, speaking ahead of the summit, conceded that the path toward greater regional integration was fraught with obstacles.
"There is a large chasm between what is said and done that we still have to overcome," he told reporters.
Security is tight at the Colombian summit
The leaders will also discuss how to boost security in a region plagued by rebel insurgencies and drug killings.
The terrorist threat was evident at the summit.
The mountain-top colonial hacienda where the talks were held was turned into a fortress, with helicopters circling above, commandos hiding in bushes and countless army road blocks set up in the surrounding area.
But in a departure from the norm, the summit's host, Colombian President Alvaro Uribe, took the wheel to drive a few of his Andean counterparts the 30 kilometres (18 miles) from Rio Negro to the summit's venue at the Quirama estate.