President Trump: ”South Korea imposes tariffs four times higher than the U.S. on military aid” ... ”It's not fair”

On the 4th (local time), US President Donald Trump claimed that "South Korea imposes higher tariffs than the US, despite receiving military aid and other assistance from the US," and called for a trade war.
In a speech to Congress held at the Capitol in Washington DC on the same day, President Trump named the EU as one of the countries that have used tariffs against the US.
After highlighting the European Union, China, Brazil, India, Mexico and Canada, he said, "Countless other countries impose tariffs that are much higher than what we impose on them.
"It's unfair to us," he said. "India imposes high auto tariffs of over 100 percent on us. China imposes on average double the tariffs we do on our products.
"And the average tariff in Korea is four times higher than in the U.S.," he said. "Just think about it. It's four times higher. We have a lot of military and various methods in Korea.
"This is happening despite our support for the US. Both our friends and our enemies do the same thing," he said. However, he did not know on what basis President Trump had said, "South Korea should impose higher tariffs than the US."
It is unclear whether the US is claiming that it is "being tariff-free" because South Korea has concluded a free trade agreement (FTA) with the US and trades many products tariff-free.