The US dispatched two long-range bombers to South Korean skies this week as a show of force in response to recent North Korean nuclear and missile tests, the US armed forces reported Wednesday.
One of the two B-1B bombers flew over a military base in Osan and then returned to its station in Guam. The second landed in Osan, according to US armed forces in Korea.
"What we are showing today is just one tool we have to choose from a wide array of options," said US Air Force Lieutenant General Thomas W Bergeson on Wednesday. "The alliance grows stronger every day and we remain prepared to defend and to preserve the security of the Korean Peninsula and the region."
He called the ties between the two nations "iron-clad."
It is not clear when the bomber that landed in Osan would leave the country.
It was the second time in a week that the US has made a show of force in support of its South Korean ally and prompted accusations from North Korea that the United States is seeking to provoke it.
In Pyongyang state media, the bombers were described as "disreputable atomic tools of death."
The United States has 28,500 soldiers stationed in South Korea.
North Korea has rattled regional nerves this month, first with a nuclear test and, this week, with the test of a rocket for launching satellites that foreign experts say could easily be repurposed for intercontinental nuclear missiles. The September 9 test was its fifth nuclear test overall and its second this year.
North Korea is under heavy UN sanctions for its pursuit of a nuclear weapons programme, primarily because its neighbours and key world powers worry that the regime would be prone to use such weapons offensively. Its recent actions have prompted debate at the United Nations about further punishment.
US President Barack Obama used his address at the UN General Assembly on Tuesday to describe North Korea as a "wasteland" and argue that its nuclear tests constitute a threat to international security.