Venezuela, Argentina and Brazil have agreed to push on with plans for a 10,000km (6,215 mile) gas pipeline from Venezuela to Argentina.
Mr Chavez urged the expansion of plans to include Bolivia.
Leaders of the three countries held a one-day summit in Sao Paulo, Brazil, to discuss the project, as well as other plans for regional integration.
Critics say the pipeline is over-ambitious and too costly.
Venezuelan President Hugo Chavez says the $20bn project, planned for 2007-2017 could create a million jobs.
At the summit, he called for the expansion of plans to include Bolivia.
Bolivia's gas reserves of 48.7 trillion sq ft (4.5 trillion sq metres) are second in the continent to Venezuela's 151 trillion sq ft (14 trillion sq metres).
"Bolivia is a priority," Mr Chavez said.
"This project will guarantee energy... for all South American countries in the 21st Century and beyond."
The regional leaders also discussed ways of solving a crisis in the Andean Community trade bloc.
Venezuela has said it is pulling out the bloc now that a number of member countries have signed trade deals with the US.
Bolivia, Cuba and Venezuela will sign a "trade agreement of the people" in Cuba on Saturday in an attempt to counter free trade agreements Latin American countries are signing with the US government, Bolivian President Evo Morales said.