According to Donald Trump, what he calls the devaluation (write-down) of the two countries' currencies strikes hard against US farmers, whose goods are traded in dollars.

"Therefore, with immediate effect, I will reintroduce customs duties on all steel and aluminum shipped to the United States from these countries," Trump writes.

Brazil's President Jair Bolsonaro has, according to Reuters, figured he can talk to Trump about upcoming tariffs.

Took the opportunity to urge the US central bank

Trump also took the opportunity to urge the US Federal Reserve to take steps to prevent countries from making the dollar stronger.

"Lower interest rates & stimulate - Fed!", He writes.

Trump has repeatedly called on the Fed's board to lower the policy rate below zero, citing, inter alia, that negative policy rates in other countries and in the euro zone provide a competitive advantage in the world market.

The Fed's next interest rate announcement will come on December 11.

Refrained from imposing duties on cars

Earlier this fall, Trump refrained from imposing tariffs on cars and car parts from Japan and the EU, which would then have happened on the grounds that cheap goods from Japan and the EU threatened US national security.

According to the legislation Trump's car tariffs would have been based on, a deadline was passed to introduce the tariffs on November 14.