The Brazilian president's statement about "a humanitarian disaster" came as the Mercosur customs union began a summit in the Brazilian city of Foz do Iguaçu on Saturday.
The US has intensified military attacks against, among other things, ships from Venezuela, which the US says have been smuggling drugs. In addition, groups said to be close to Venezuela's totalitarian leader Nicolás Maduro have been placed on the US terror list. The US has also strengthened its military presence off the coast of Venezuela.
Maduro claims the US is trying to overthrow him.
Brazil's president, with a political affiliation on the left, chose to indirectly accuse foreign powers of influencing developments in Latin American countries.
Four decades after the Falklands War, the South American continent is again threatened by a military presence, said President Lula, referring to the war between Britain and Argentina over the Falklands Islands in 1982.
The division within the Mercosur customs union was clear, however, when member country Argentina's leader, Javier Milei, praised US President Donald Trump's pressure on Venezuela to "liberate the people of Venezuela" in his speech immediately after the Brazilian leader's opening speech.
Venezuela has been temporarily suspended from Mercosur.
President Trump said in an interview with the media company NBC earlier this week that he does not rule out the possibility of a war breaking out between the United States and Venezuela.
