President Donald Trump tweeted on Friday morning that North Korea has been "behaving very badly" and that China has done little to contain the threat.
"North Korea is behaving very badly,"Trump wrote. "They have been 'playing' the United States for years. China has done little to help!"
The tweet comes as Rex Tillerson, Trump's secretary of state, is on a trip to Asia.
While Tillerson was in South Korea on Friday, he said that if North Korea elevated "the threat of their weapons program to a level that we believe requires action," a military response from the US would be on the table.
Tillerson also urged China, an ally of North Korea, to fully implement sanctions the United Nations imposed on North Korea for its nuclear weapons program and missile tests. He heads to Beijing next.
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