The U.S. deployed a B-52 bomber on a low-level flight over its ally South Korea on Sunday, a show of force following North Korea's nuclear test last week.
North Korean leader Kim Jong Un maintained that Wednesday's test was of a hydrogen bomb and said it was a self-defensive step against a U.S. threat of nuclear war.
North Korea's fourth nuclear test angered both China, its main ally, and the United States, although the U.S. government and weapons experts doubt the North's claim that the device was a hydrogen bomb.
The massive B-52, based in Guam and capable of carrying nuclear weapons, could be seen in a low flight over Osan Air Base around 0300 GMT. It was flanked by two fighter planes, a U.S. F-16 and a South Korean F-15, before returning to Guam, the U.S. military said in a statement.
"The United States remains steadfast in its commitment to the defense of South Korea and to maintaining stability on the Korean Peninsula, to include extended deterrence provided by our conventional forces and our nuclear umbrella," said U.S. Lt. Gen. Terrence O'Shaughnessy.
The United States is also considering sending a nuclear-powered aircraft carrier to waters off the Korean peninsula in February to join a naval exercise with Seoul, South Korea's Yonhap news agency reported without identifying a source. However, U.S. Forces Korea officials said they had no knowledge of the plan, according to Reuters. - Idrak