Luiz Inácio da Silva has announced he will run for a fourth term as Brazil's president in the nation's elections in 2026.

The 79-year-old had indicated during his last election campaign that it would be his last - but stressed he did not feel his age in comments during a state visit to Indonesia on Thursday.

"I'm about to turn 80 years old, but you can be sure I have the same energy I had when I was 30. And I will run for a fourth term in Brazil," Lula told reporters.

The decision to run comes despite Lula suffering health problems in office after winning in the tightest run-off election in the South American nation's history.

Already Brazil's oldest president when inaugurated, in December last year he underwent surgery for a brain bleed caused by a blow to the head he sustained in a fall in the presidential palace.

The left-wing leader beat then-incumbent Jair Bolsonaro by 51% to 49% in 2022.

The right-wing former president is unlikely to be able to challenge Lula again, as he is serving a 27-year sentence for plotting a military coup aimed at keeping him in power after he lost the last election.

The legal case which led to his lengthy sentence has drawn the ire of US President Donald Trump, prompting him to impose a 50% tariff on imports of Brazilian goods.

However, the two described having a "friendly" call earlier in October as Lula seeks to reduce those levies, and are expected to meet on Sunday.

Lula, who turns 80 on Monday, has himself been imprisoned - for 18 months on corruption charges - but was freed in 2018 after the case was overturned.

He has hinted at a possible fourth run for president since returning to office, but had so far stopped short of a formal announcement.

Brazil's constitution limits presidents to two consecutive terms. Lula previously served a two-term stint between 2003 and 2011.