Trump also urged the Federal Reserve to prevent countries from taking advantage of a strong dollar by devaluing their currencies.
Brazilian President Jair Bolsonaro, pictured with Donald Trump at the White House last March, said Monday he would call Trump about his tariff tweet and was "almost certain" the US president would listen.
"If needed, I can also talk to Trump, I have an open channel with him", he added as he left the presidential palace.
Brazil is grappling with stubborn double-digit unemployment, and its economy is headed toward its third straight year of roughly 1% growth, following two years of deep recession. Macri lost his re-election bid in October and will leave office on December 10.
Trump has repeatedly urged the US central bank to lower rates to below zero, arguing that negative rates in Europe and elsewhere give those countries a competitive advantage.
According to Reuters, inflation in Argentina is now at its second lowest level since March 1999.
Trump has repeatedly criticized Fed chairman Jerome Powell for not cutting interest rates as much as the Republican president would like.
At its most recent meeting, in October, the Federal Reserve cut short-term interest rates for a third time this year to try to support the USA economy.
In the case of Argentina, soybean shipments to China totaled $2.4 billion in 2017, more than triple the value of the South American nation's aluminum and iron pipe exports to the U.S. As the trade war between Beijing and Washington escalated, China boosted imports of the oilseed to $2.5 billion in the first 10 months of 2019, Chinese customs data show.
In a second Twitter post, Trump signaled that he wants the US central bank to do something about suppressed currencies.
He also has earmarked almost $30 billion for farmers to help make up for their losses.
He also touted the economic boom since imposing sweeping tariffs on steel and aluminum imports previous year.
Shares of the Pittsburgh company are down 43% over the past year.