Antony Blinken saidthat the US joined Lula in calling for an immediate end to the attacks.
US President Joe Biden on Sunday said the situation in Brazil was "outrageous" after supporters of far-right former President Jair Bolsonaro invaded the country's Congress, presidential palace and Supreme Court.
Leftist President Luiz Inacio Lula da Silva, who defeated Bolsonaro in the most fraught election in a generation last year, announced a federal security intervention in Brasilia lasting until Jan. 31 after capital security forces initially were overwhelmed by the invaders.
US National Security Advisor Jake Sullivan said the United States condemns any effort to undermine democracy in Brazil.
"President Biden is following the situation closely and our support for Brazil's democratic institutions is unwavering. Brazil's democracy will not be shaken by violence," Sullivan said on Twitter.
US Secretary of State Antony Blinken said on Twitter that the United States joined Lula in calling for an immediate end to the attacks.
The violence echoed the US Capitol invasion two years ago by supporters of former President Donald Trump.
"I condemn this outrageous assault on #Brazil's govt buildings incited by demagogue Bolsonaro's reckless disregard for democratic principles," US Senator Bob Menendez, chairman of the Senate Foreign Relations Committee, said on Twitter.
"2 yrs since Jan. 6, Trump's legacy continues to poison our hemisphere. Protecting democracy & holding malign actors to account is essential."
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