It follows North Korea’s successful launch of an intercontinental ballistic missile that travelled about 1,000km in the air before landing in the sea off Japan.
Two American B-1 bombers have now flown to the region and were escorted by South Korean fighter jets as they performed a low-pass over an air base near the South Korean capital, Seoul.
Meanwhile, General Terrence J. O’Shaughnessy, Pacific Air Forces commander, said: ‘If called upon, we are ready to respond with rapid, lethal, and overwhelming force at a time and place of our choosing.’
He added that North Korea is ‘the most urgent threat to regional stability’.
He said: ‘Diplomacy remains the lead. However, we have a responsibility to our allies and our nation to showcase our unwavering commitment while planning for the worst-case scenario.’
Flight data from North Korea’s recent missile test indicates that parts of the USA, including Los Angeles and Chicago, are within range of Pyongyang’s weapons.
But the US has also conducted its own successful missile test.
A Terminal High Altitude Area Defense, or THAAD, system, launched successfully over the Pacific Ocean from Alaska, the US Missile Defense Agency said.
Vice President Mike Pence has again called for North Korea to end its nuclear programme.
He said: ‘The continued provocations by the rogue regime in North Korea are unacceptable and the United States of America is going to continue to marshal the support of nations across the region and across the world to further isolate North Korea economically and diplomatically.
‘But the era of strategic patience is over. The president of the United States is leading a coalition of nations to bring pressure to bear until that time that North Korea will permanently abandon its nuclear and ballistic missile programme.’