The two men highlighted the importance of their countries' defense partnership during a time of major global unrest, at a ceremony at Brazil's ultra-modern naval base in Itaguai near Rio de Janeiro.

It is here that Brazil built the Tonelero, the third of four planned conventional diesel attack submarines, with training, equipment, and technical assistance from France.

Under cloudy skies, the submarine was christened by First Lady Rosangela da Silva, nicknamed "Janja."

France and Brazil's defense ties "will allow two important countries, each on a continent, to prepare so that we can face this adversity, without worrying about any type of war, because we are defenders of peace," said Lula.

Despite differences, notably on the Ukraine war, Macron said "the great peaceful powers of Brazil and France" had "the same vision of the world."

Macron is on a whirlwind tour of Brazil, a major economic ally, which kicked off Tuesday with the launch of a plan to raise over a billion dollars in green investments to protect the Brazilian and Guyanese Amazon.

- Jungle bromance -

The visit, the first by a French president to Latin America's economic giant in over a decade, is also a move to reset ties which had deteriorated significantly under former president Jair Bolsonaro.

A warm meeting between Macron and Lula in the Amazon, in which the two men were pictured beaming and clasping hands in the jungle, spawned a raft of internet memes about their bromance.

The cozy scenes -- a far cry from the days Bolsonaro lobbed insults at Macron's wife -- continued Wednesday at the submarine launch.

With its 8,500 kilometers of coastline, Brazil is seeking to ensure the security of what it calls the "blue Amazon," its immense exclusive economic zone through which more than 95 percent of its foreign trade passes and where it extracts 95 percent of its oil.

The construction of the submarines was outlined in a 2008 deal between Lula and former French president Nicolas Sarkozy, which also included the purchase of 50 Caracal helicopters.

The fourth submarine, the Angostura, will be launched in 2025.

- France skirts around nuclear sub -

Brazil is also planning to build its first nuclear-powered submarine, the Alvaro Alberto, a project that has suffered significant delays, mainly due to budget constraints.

The French naval defense manufacturer Naval Group is supporting the design and construction of the submarine, except for the nuclear boiler which is being designed by the Brazilians.

Brasilia is however trying to convince Paris to increase technology transfers to help it integrate the reactor into the submarine and sell it equipment linked to nuclear propulsion.

France has been reticent to transfer such technology due to the challenges of nuclear proliferation.

"If Brazil wants to have access to knowledge of nuclear technology, it is not to wage war. We want this knowledge to assure all countries that want peace that Brazil will be at their side," said Lula.

Macron told Brazil "France will be at your side" during the development of the nuclear-powered submarines, without announcing specific assistance.

"I want us to open the chapter for new submarines... that we look nuclear propulsion in the face while being perfectly respectful of all non-proliferation commitments," he said.

Later on Wednesday, Macron arrived in the economic capital Sao Paulo to promote his country to Brazilian investors.

France is the third largest investor in Brazil, with more than 40 billion euros in direct investments in the country.

"Brazil is not up to par in terms of investment in France when you see the size and expertise of Brazilian conglomerates," said the Elysee presidential palace.

On Thursday Lula will welcome Macron to the Planalto presidential palace in the capital Brasilia.