Environmentalists have heavily criticised the exploratory drilling in the sea off the mouth of the Amazon.
Javier Milei spoke at a campaign rally for right-wing presidential candidate Flávio Bolsonaro, who is running against Lula.
Eduardo Bolsonaro called the conviction "baseless and senseless".
The US and Brazilian presidents did not appear together publicly, but traded compliments after their talks.
The two leaders have a strained relationship and will be closely watched for signs of a breakthrough over tariffs and other issues.
Last year ex-president Jair Bolsonaro was sentenced to 27 years in jail for plotting a coup after losing an election.
Former President Jair Bolsonaro was moved from his cell to hospital earlier this month with pneumonia.
Rio de Janeiro's iconic Carnival parades began with a tribute to Brazil's President Lula, illustrating his rise from poverty to power.
The former leader is serving a 27-year sentence for plotting a coup after losing the 2022 presidential election.
