But he said they were personal opinions and not a position of the government. Brazil's constitution prohibits nuclear weapons.
'No nuclear arms'
A spokesman for Luiz Inacio Lula da Silva, the Brazilian president, told the Associated Press news agency that Alencar's comments "do not reflect the position of the government".
Nevertheless, the remarks came on the same day that the UN Security Council voted unanimously for a strategy aimed at halting the spread of nuclear weapons and ultimately eliminating them.
Brazilian officials have promoted nuclear-generated electrical power and say they plan to build a nuclear-propelled submarine.
But Nelson Jobim, the defence minister, reiterated as recently as August that Brazil has no interest in nuclear weapons.
Alencar, who is not a member of the ruling party, sometimes expresses positions at odds with Silva's, David Fleischer, a political scientist at the University of Brasilia, said.
Fleischer said Brazil abandoned efforts to develop nuclear weapons about 25 years ago when the military ceded control of the country to civilians.
Brazil has also signed the 1988 Tlatelolco Treaty that bars nuclear arms in South America.