Brazilian President Lula da Silva vowed to trigger Brazil's reciprocity law if negotiations with the U.S. fail.

That is the highest levy announced so far in Trump’s letters to world leaders this week, and comes after he wrote a lengthy message supporting the former Brazilian leader.

Brazil’s President forcefully rebuked Trump after the U.S. leader called the prosecution of Lula’s predecessor, Bolsonaro, a “witch hunt” and hiked tariffs on the Latin American nation.