North Korean military personnel are reportedly preparing for their winter training exercises as three USA aircraft carriers lurk near the Korean Peninsula in an unprecedented show of force by Washington's navy.
It is the first time three of the 100,000-ton behemoths have sailed together in the Western Pacific together in a decade.
Trump, who is on the final leg of his crucial Asia tour, made North Korea a top priority in his 12-day-long trip.
Mr Ja said the United States had reactivated round-the-clock sorties by B-52 strategic bombers and was making frequent flights of B-1B and B-2 bombers in the air space of South Korea, AFP reported. "The combined drills are to present our resolve and will to deter North Korea's provocations and retaliate if provoked", Yonhap news agency quoted a South Korean official as saying.
North Korean government officials told CNN's Will Ripley in Pyongyang last week that the U.S. was increasingly taking action that could "ignite another Korean War".
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The Philippines is about too far but, you know, nobody will save us from a holocaust if it happens", he added. He also proposed that Japan and China cooperate in doing business in third countries.
Japan's Maritime Self-Defense Force held a joint exercise with the US strike groups on November 12. The Reagan - homeported in Japan - joined the other two carriers, which are based in the Western United States.
"The goal of the drill in worldwide waters is to showcase the U.S. Navy's "unique capability to operate multiple carrier strike groups as a coordinate strike force effort", the service said in a statement".
"The JMSDF is always using every opportunity to strengthen the JMSDF-USN alliance, and joining an exercise like this is a natural event to stabilize regional security", a statement from the Maritime Self-Defense Force said.
The South Korea conducted the exercise with seven vessels including three destroyers. Three aircraft carrier strike groups have last operated together in the Western Pacific during exercise Valiant Shield off the coast of Guam in 2006 and 2007 respectively.
"The exercise is aimed at enhancing deterrence against North Korea's nuclear and missile threats and showing off preparedness to fend off any provocative acts by the North", a South Korean defence ministry spokesman said.