The United States flew a long-range bomber in a trilateral drill with South Korea and Japan on Sunday in response to North Korea's recent test-firing of a new intercontinental ballistic missile designed to strike the US mainland, South Korea's military said.

North Korea on Thursday tested the newly developed Hwasong-19 ICBM, which flew higher and stayed in the air longer than any other missile it has fired. North Korean leader Kim Jong Un called it “an appropriate military action” to cope with external security threats posed by its rivals.

On Sunday, the US flew the B-1B bomber to train with South Korean and Japanese fighter jets near the Korean Peninsula, demonstrating the three countries' firm resolve and readiness to respond to North Korea's advancing nuclear and missile programs, South Korea's Joint Chiefs of Staff said in a statement.

The trilateral aerial training was the second by South Korea, the U.S. and Japan this year, the statement said.

The US often responds to major North Korean missile tests with temporary deployments of some of its powerful military assets such as long-range bombers, aircraft carriers and nuclear-powered submarines to and near the Korean Peninsula. North Korea typically responds angrily to such U.S. actions, calling them part of a U.S.-led plot to invade the North and performing additional weapons tests.

The US has flown the B-1B bomber over or near the Korean Peninsula four times this year, according to South Korea's military. A B-1B is capable of carrying a large conventional weapons payload.

Thursday's Hwasong-19 test, North Korea's first ICBM test-firing in almost a year, showed progress in North Korea's missile program. But many experts say North Korea still has some technological issues to master to acquire functioning ICBMs that can deliver nuclear strikes on the U.S. mainland. The experts say the Hwasong-19 shown in North Korea's state media photos and videos looked too big to be useful in a war.

The ICBM test was seen as an effort to grab American attention ahead of the U.S. presidential election this week and respond to international condemnation of North Korea's reported dispatch of thousands of troops to Russia to support its war against Ukraine, observers say.