On Sunday, North Korea test-fired a ballistic missile from a mobile launcher, signaling advancement in its capabilities as it develops nuclear weapons and the means to deliver them.
South Korea and Japan, both hosts to tens of thousands of U.S. forces, are within range of North Korean missiles. Washington, under the Obama administration, nudged Seoul and Tokyo to set aside historical acrimony and work closer together in the face of the common threat.
U.S. Secretary of State Rex Tillerson, left, and China's Foreign Minister Wang Yi talk before an opening session meeting of the G20 foreign ministers at the World Conference Center in Bonn, Germany, Thursday, Feb. 16, 2017.
Photo Credit: Brendan Smialowski/AP, pool
In 2014, the three nations signed a pact on joint intelligence-sharing about North Korea's nuclear and missile programs. Although relations remain tense, South Korea and Japan in November agreed to share sensitive information bilaterally as well.
President Donald Trump this week vowed to "deal with" North Korea, calling it "a big, big problem." But he has not spelled out how he intends to do so. Experts say that North Korea will likely gain the capacity to reach the U.S. mainland with nuclear weapons in the next few years.