Jair Bolsonaro has avoided conceding defeat in his first remarks since losing his bid for re-election – but an aide said he would begin the transition of power.
The outgoing Brazilian president was beaten by his left-wing rival, Luiz Inacio Lula da Silva, in the run-off on Sunday.
In the closest contest since Brazil returned to democracy in 1985, Mr da Silva won 50.9% to Mr Bolsonaro’s 49.1%.
Mr Bolsonaro did not directly concede defeat or congratulate his rival, but his chief of staff, Ciro Nogueira, said they would begin the process of a transition to Mr da Silva’s government.
A far-right politician often described as Brazil’s Donald Trump, Mr Bolsonaro had not spoken until now.
In a brief address from the presidential palace, he thanked his supporters and said he will “continue to follow the constitution”.
He said: “I have always been labelled as anti-democratic and, unlike my accusers, I have always played within the four lines of the constitution.”
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In recent days truck drivers and other supporters of Mr Bolsonaro have blocked hundreds of roads across the country.
They have disrupted fuel and meat distribution and hampered the country’s ability to send grains to port, companies and authorities have said.
They argue the election has been fraudulent and some called for military intervention to keep Mr Bolsonaro in power and for Congress and the Supreme Court to be disbanded.
Mr Bolsonaro said the protests were the fruit of “indignation and a sense of injustice” over the vote.
Mr da Silva, known in the country simply as “Lula”, has promised to govern beyond his party by bringing in centrists and even some right-leaning people who voted for him for the first time.
However, he will likely face strident opposition from more conservative politicians in the increasingly politically polarised country.