In a tweet posted just after 6 a.m., Trump said the countries have been "presiding over a massive devaluation of their currencies" which he says is bad for American farmers.
Trump also urged the Federal Reserve to lower interest rates so countries "no longer take advantage of our strong dollar". Trump says that by these and other nations deliberately devaluing their currencies, "this makes it very hard for our (manufacturers) & farmers to fairly export their goods", he wrote.
Jair Bolsonaro, the Brazilian president, a Right-wing populist seen as a Trump ally, said he hoped the president. He announced the actions in a tweet and in doing so, criticized the Fed for not devaluing the dollar by lowering rates and loosening policy.
Both South American countries have benefited from the USA trade war with China.
Tariffs against the countries were implemented in March 2018 but they were removed about five months later.
The president also took a swipe at the Federal Reserve.
Labelled by friends and foes as "Trump of the tropics", the far-right leader has boasted his relationship with the American president as a cornerstone of his diplomacy.
"Their economy is not comparable with ours; it's many times bigger". But it recovered to trade stronger at 4.2230 per USA dollar.
Shares in Brazil's Gerdau SA, Usiminas and Cia Siderurgica Nacional SA were up 0.5 percent, 1.4 percent and 1.5 percent in mid-morning trade, respectively. A source familiar with Brasilia's reaction rejected the US claim of currency manipulation, noting the central bank was working to lift the real.
Both South American nations were among a group of US allies that Trump had exempted from steel and aluminum tariffs in March 2018.
Montreal faces Philadelphia on 5-game home slide
Detroit cashed in on the second of those opportunities, jumping out to a 1-0 lead on a Robby Fabbri power-play goal at 11:47. Additionally, the Provorov and Matt Niskanen pairing were nothing short of stellar for the Flyers yet again.