Brazil is building five submarines to patrol its massive coast, including one powered by an atomic reactor that would put it in the small club of countries with a nuclear sub.
The South American giant is exploring major oilfields offshore that could make it a top petroleum exporter.
The new submarines aim to protect that resource, the navy official coordinating the US$10 billion project, Gilberto Max Roffe Hirshfeld, said.
"The nuclear-propelled submarine is one of the weapons with the greatest power of dissuasion," he said. "Brazil has riches in its waters. It's our responsibility to have strong armed forces. Not to make war, but to avoid war, so that no one tries to take away our riches."
The project is a joint venture between the navy, Brazilian construction firm Odebrecht and French state defence firm DCNS.
Brazil and France signed a deal for the project in 2008 under which DCNS is providing building materials and training while Brazil builds up its own submarine industry.
Brazil is developing the nuclear reactor and enriched uranium itself.
The first submarine, a conventional sub called SBR1, is 45 per cent complete and scheduled to launch in 2017. The second is in the early stages of construction and is due to launch in 2019. Work on the nuclear sub, SNBR, is supposed to start in 2017, with a launch target of 2025, the year the project wraps up.
When complete, the nuclear submarine will be 100 metres long and weigh 6,000 tonnes. Its conventional cousins will be slightly smaller, at 75 metres and 2,000 tonnes.
The only countries now designing and building their own nuclear submarines are the permanent members of the United Nations Security Council - Britain, China, France, Russia and the United States - plus India.