Rio de Janeiro. Brazilian President Luiz Inácio Lula da Silva said Thursday that he will impose retaliatory tariffs on the United States if President Donald Trump follows through on a pledge to boost import taxes by 50 percent over the South American country's criminal trial against his predecessor, Jair Bolsonaro.

Lula said he will trigger Brazil's reciprocity law approved by Congress earlier this year if negotiations with the United States fail.

"If there's no negotiation, the reciprocity law will be put to work. If he charges 50 percent tariffs from us, we will charge 50 percent from them," Lula told TV Record in excerpts of an interview that will be fully aired later in the day. "Respect is good. I like to offer mine and I like to receive it."

Lula's comments raise the risk of a tariff war erupting between the two countries, similar to what has happened between the US and China. Trump has vowed to respond forcefully if countries seek to punish the US by adding tariffs of their own.

The president of Brazil's Senate, Sen. Davi Alcolumbre, and Chamber of Deputies Speaker Hugo Motta, a pair of moderates who have recently been at odds with Lula, agreed that the reciprocity law gives Brazil "the means ... to protect our sovereignty."

"We will be ready to act with balance and firmness in defense of our economy, our productive sector, and the protection of Brazilian jobs," they said in a joint statement.

A New Front in the Trade War
The tariffs letter that Trump sent to Brazil -- and posted on social media Wednesday -- railing against the "witch hunt" trial against Bolsonaro opened up a new front in his trade wars, with the US leader directly using import taxes to interfere with another nation's domestic politics.

Trump has already tried to use tariffs to ostensibly combat fentanyl trafficking and as a negotiating tool to change how other nations tax digital services and regulate their economies.

In Brazil's case, Trump is trying to dictate the outcome of the criminal trial of Bolsonaro, an ally who, like Trump, has been charged with attempting to overturn a presidential election. Bolsonaro maintains that he is being politically persecuted by Brazil's Supreme Court over his charges on the alleged plot to remain in power after his 2022 election loss to Lula.

"There's nothing Lula or Brazil can do about Bolsonaro's trial," said Carlos Melo, a political science professor at Insper University in Sao Paulo. "Any change in that would be Brazil's capitulation. Bolsonaro's situation here won't change. How do you negotiate over that?"

Lula ordered his diplomats on Thursday to return Trump's letter if it physically arrives at the presidential palace in Brasilia. The document attacks the country's judiciary and mentions recent rulings on social media companies among the reasons why goods from the South American nation will have higher tariffs from Aug. 1.