The US has imposed sanctions on Viviane Barci de Moraes, wife of Brazilian Supreme Court Justice Alexandre de Moraes, ratcheting up diplomatic tensions following former president Jair Bolsonaro's conviction for coup plotting.

The sanctions, announced on September 22 under the Magnitsky Act introduced by the Obama administration in 2012 to target shady Russian operatives, freeze any US assets belonging to Moraes' wife and bar US financial institutions from conducting dollar transactions with her, potentially affecting credit card operations through Mastercard and Visa networks.

According to Jornal de Brasília, Moraes responded defiantly to the US move, stating Brazil's judiciary would not accept external pressure.

"The illegal and lamentable application of the Magnitsky Act to my wife not only contrasts with the history of the US of America, of respect for law and fundamental rights, but also violates International Law, Brazil's sovereignty, and the independence of the judiciary," he said in a statement.

"Independence of the judiciary, institutional courage and defence of national sovereignty are part of the republican universe of Brazilian judges, who will not accept coercion or obstruction in the exercise of their constitutional mission conferred sovereignly by the Brazilian people."

In July, Moraes himself was sanctioned by the US State Department "for serious human rights abuse, including arbitrary detention involving flagrant denials of fair trial guarantees and violations of the freedom of expression."

Brazil's Supreme Court issued its own statement branding the sanctions as unjust and based on false narratives, and arguing that nearly all Brazilians recognise the "historical importance of a trial and punishment for an attempted coup d'état."

Meanwhile, the Brazilian parliament’s ongoing negotiations about January 8, 2023 riot prosecutions could slow down, according to former president Michel Temer, as reported by CNN Brasil.

"The gesture of today, penalising the wife of Justice Alexandre de Moraes, is not conducive to the atmosphere of dialogue we've seen in recent days," he said in an interview with CNN Brasil.

Temer revealed discussions about possible legislative measures, including sentence reductions or limited amnesty for January 8 participants. Among proposals under consideration is a constitutional modification establishing eight-year ineligibility periods for those involved in the events. Tens of thousands of Brazilians took to the street on September 21 protesting congressional moves that could shield lawmakers from prosecution and grant amnesty to Bolsonaro and his attempted coup supporters.

Fellow Supreme Court justices rallied behind Moraes following the sanctions announcement. Justice Flávio Dino expressed solidarity whilst lamenting damage to Brazil-US relations.

"I regret that centuries of good cultural relations between Brazil and the US are being affected in such an absurd way," he wrote on social media, as quoted by Jornal de Brasília.

Prosecutor-General Paulo Gonet accused Jair Bolsonaro's son Eduardo, who currently lives in the US, of relentlessly lobbying the Trump administration to punish Brazilian officials involved in his father's case.

“The entire strategic plan outlined confirms the specific intent of Eduardo Bolsonaro and [conservative blogger] Paulo Figueiredo to bring about instability and fear, projecting onto Brazilian authorities the prospect of foreign reprisals and onto the population the spectre of an isolated and ridiculed country,” Gonet stated, as quoted by Agencia Brasil.

For his part, Treasury Secretary Scott Bessent defended the punitive measures using provocative language, comparing Moraes and his wife to Depression-era criminals Bonnie and Clyde.

"There is no Clyde without Bonnie," Bessent said as quoted by Reuters, referencing the notorious bank-robbing duo killed by police in 1934.

Echoing the rhetoric of US President Donald Trump, Bessent accused Moraes of conducting "an oppressive campaign of censorship, arbitrary detentions and politicised processes" including against Bolsonaro.

The State Department issued additional warnings about protecting "malicious foreign actors like Moraes," stating that supporters "threaten US interests and will also be held accountable."

Additional visa restrictions targeting Brazilian officials are anticipated in response to Bolsonaro's conviction, with some of the expected targets including Attorney General Jorge Messias, Federal Police Director Andrei Rodrigues, delegate Fabio Shor, and judges Airton Vieira and Marco Antônio Vargas, who assisted Moraes in cases involving the former president.

The escalating measures reflect a deepening US-Brazil rift following Bolsonaro's 27-year prison sentence for coup plotting, creating diplomatic complications that extend beyond individual sanctions to broader bilateral relationships between the two largest Western Hemisphere democracies.

This week, Brazilian officials reported that they have had difficulty obtaining US visas to attend the UN’s General Assembly in New York.