(From CNN) U.S. President Donald Trump announced Monday that the US will “restore” steel and aluminum tariffs on Brazil and Argentina, citing a “massive devaluation of their currencies.”

The United States has bought more steel from Brazil than any other country besides Canada during the first nine months of this year

“Brazil and Argentina have been presiding over a massive devaluation of their currencies. which is not good for our farmers. Therefore, effective immediately, I will restore the Tariffs on all Steel & Aluminum that is shipped into the U.S. from those countries,” Trump tweeted early Monday morning from Washington.

Both Brazil and Argentina were exempted from 25% steel and 10% aluminum tariffs last year when Trump was attempting to avoid a trade war with those countries.

Both Argentina and Brazil have benefited from warmer trade relations with the US under Trump as a result of the US-China trade war, but the two countries have recently seen the values of their currencies drop.

The Brazilian real is down more than 8% against the dollar this year, and the Argentine peso is down 37%.

The United States has bought more steel from Brazil than any other country besides Canada during the first nine months of this year, making up nearly 11% of all steel imports, according to Census Bureau data. It relies on Argentina much less for steel, which made up for less than 1% of imports.