The United States flew two nuclear-capable B-1B bombers over South Korea on Tuesday in a forceful response to North Korea's latest nuclear test last week.
That show of power designed to reassure ally South Korea was also accompanied by the dispatch of Sung Kim, the U.S. special envoy for North Korean policy, to Seoul, where he met South Korean officials on Tuesday.
The Associated Press said one of its photographers witnessed the supersonic B-1B bombers escorted by U.S. and South Korean jets as they flew over Osan Air Base, a U.S. facility which is 75 miles (120 kilometers) from the South's border with North Korea. The bombers were expected to return to Andersen Air Force Base in Guam without landing in South Korea, the AP reported.
"The United States and the Republic of Korea are taking actions every day to strengthen our Alliance and respond to North Korea's continued aggressive behavior," said General Vincent K. Brooks, U.S. Forces Korea commander, in a statement issued by the U.S. military in Seoul.
"Today's demonstration provides just one example of the full range of military capabilities in the deep resources of this strong alliance to provide and strengthen extended deterrence. The Alliance military forces remain ready to meet mutual defense obligations against threats to the security of the Korean Peninsula and the region," said Brook after a meeting with General Lee Sun-jin, chairman of South Korea's Joint Chiefs of Staff.
North Korea conducted its fifth and largest nuclear test on Friday, the 68th anniversary of the state's founding, near its Punggye-ri nuclear site in North Hamgyong province in the country's northeastern region, where the detonation triggered a 5.3-magnitude earthquake. Later, it reported that it had successfully tested a nuclear warhead that could be mounted on a missile.
The nuclear test was the country's fifth in the past decade and the third under Kim Jong Un, who came to power in 2012 and has sought to build up the country's nuclear capabilities. The North's previous nuclear tests were conducted in 2006, 2009, 2013, and January of this year.
"North Korea's nuclear test is a dangerous escalation and poses an unacceptable threat," said Gen. Brooks. "The United States has an unshakable commitment to defend allies in the region and will take necessary steps to do so, including operations like this one today."
Nuclear expert Siegfried Hecker wrote on the North Korea-focused U.S. website 38 North that Pyongyang has a stockpile of fissile material sufficient to make some 20 nuclear bombs by the end of this year and could add approximately sever per year.
"Left unchecked, Pyongyang will likely develop the capability to reach the continental United States with a nuclear tipped missile in a decade or so. Much more troubling for now is that its recent nuclear and missile successes may give Pyongyang a false sense of confidence and dramatically change regional security dynamics," he wrote.
"More bombs and better bombs also increase the potential of accidents and miscalculations with greater consequences as the number and sophistication of bombs increase," added Hecker, who has toured North Korean nuclear facilities.