Analysts had estimated that the North’s first ICBM test on July 4 could reach Alaska, and that the latest missile appeared to extend that range significantly.

North Korean leader Kim Jong Un on Saturday said the second flight test of an intercontinental ballistic missile (ICBM) demonstrated that a wide swath of the United States, including Los Angeles and Chicago, is now in range of North Korean weapons.

The Korean Central News Agency (KCNA) said that Mr. Kim expressed “great satisfaction” after the Hwasong-14 missile reached a maximum height of 3,725 kilometers (2,314 miles) and traveled 998 kilometers (620 miles) before accurately landing in waters off Japan. The agency said that the test was aimed at confirming the maximum range and other technical aspects of the missile, it says, is capable of delivering a “large-sized, heavy nuclear warhead.”

Analysts had estimated that the North’s first ICBM test on July 4 could reach Alaska, and that the latest missile appeared to extend that range significantly.

Immediately after the launch, U.S. and South Korean forces conducted live fire exercises. South Korean Defense Minister Song Young-moo called for the deployment of strategic U.S. military assets, which usually means stealth bombers and aircraft carriers as well as additional launchers of an advanced U.S. anti-missile system.

Japanese government spokesman Yoshihide Suga said the missile, launched on late Friday night, flew for about 45 minutes, about five minutes longer than the first. The missile was launched on very high trajectory, which limited the distance it travelled, and landed west of Japan’s island of Hokkaido.

The KCNA quoted Mr. Kim as saying that the launch reaffirmed the reliability of the country’s ICBM system and an ability to fire at “random regions and locations at random times” with the “entire” U.S. mainland now within range. The agency said the test confirmed important features of the missile system, such as the proper separation of the warhead and controlling its movement and detonation after atmospheric re-entry.

Mr. Kim said the launch sent a “serious warning” to the U.S., which has been “meaninglessly blowing its trumpet” with threats of war and stronger sanctions, the KCNA said. The North Korean flight data was similar to assessments by the U.S., South Korea and Japan.

David Wright, a physicist and co-director of the global security program at the Union of Concerned Scientists, said that if reports of the missile’s maximum altitude and flight time are correct, it would have a theoretical range of at least 10,400 kilometers (about 6,500 miles). That means it could reach Los Angeles, Denver or Chicago, depending on variables such as the size and weight of the warhead that would be carried atop such a missile in an actual attack.

President Donald Trump issued a statement condemning the missile test as a threat to the world, and rejecting North Korea’s claim that nuclear weapons ensure its security. “In reality, they have the opposite effect,” he said. The weapons and tests “further isolate North Korea, weaken its economy, and deprive its people,” he said. Mr. Trump vowed to “take all necessary steps” to ensure the security of the U.S. and its allies.

Washington and its allies have watched with growing concern Pyongyang making significant progress toward its goal of having all of the U.S. within range of its missiles to counter what it labels as U.S. aggression. There are other hurdles, including building nuclear warheads to fit on those missiles and ensuring reliability. But many analysts have been surprised by how quickly leader Kim Jong Un has developed North Korea’s nuclear and missile programs despite several rounds of U.N. Security Council sanctions that have squeezed the impoverished country’s economy.

Mr. Trump has said he would not allow North Korea to obtain an ICBM that can deliver a nuclear warhead. But this week, the Defense Intelligence Agency reportedly concluded that the North will have a reliable ICBM capable of carrying a nuclear weapon as early as next year, in an assessment that trimmed two years from the agency’s earlier estimate.

Japanese Prime Minister Shinzo Abe called the launch a “serious and real threat” to the country’s security.