"What the president is doing is sending a strong message to North Korea in language that Kim Jong-Un would understand, because he doesn't seem to understand diplomatic language," Tillerson said.
Tillerson was talking to journalists aboard his plane en route to the US territory of Guam, where North Korea had warned it was considering missile strikes.
President Trump said Wednesday the United States' nuclear arsenal was now "more powerful than ever before" in a fresh warning to North Korea over its missile tests.
"My first order as President was to renovate and modernize our nuclear arsenal. It is now far stronger and more powerful than ever before," Trump wrote on Twitter before adding that "hopefully we will never have to use this power."
