"North Korea is capable of continuing to develop longer-range missiles", Physicist David Wright, told CBS News, adding that the regime's longest-distance test to date shows they are inching closer to a missile capable of reaching the USA mainland. "So if their ICBM has three stages and this is a single-stage missile, maybe we're watching the North Koreans test the first stage of what will be a multiple-stage ICBM".
It adds that the missile can carry a heavy nuclear warhead.
It was referring to a nuclear test site in the northeastern mountainous region where the North conducted its five previous nuclear tests, including two past year.
The missile would have flown about 4,500 kilometers at maximum trajectory, he wrote.
The U.N. Security Council on Monday decried North Korea's last two ballistic missile launches that took place in April and May as further violations of past sanctions resolutions imposed on the country.
Some experts said the missile, which was launched at a high angle, would have the same reach as an intercontinental ballistic missile if it were fired at a 30 to 45-degree angle.
It was the regime's most successful missile test to date, but officials in in South Korea said more information was needed before the North's inflammatory claim about nuclear warheads could be confirmed.
New South Korean President Moon Jae-in met Matt Pottinger, overseeing Asian affairs at the U.S. National Security Council, on Tuesday and afterwards South Korea's presidential Blue House announced that Moon would meet Trump in Washington next month.
The regime of President Kim Jong-un successfully test-fired a medium-range ballistic missile on Sunday that the U.S. military said landed about 60 miles off Russia's east coast.
The Korean Central News Agency has calledNorth Korea's new missile a "ground to ground medium to long-range ballistic missile".
Outsiders express more skepticism about North Korea's nuclear warhead claims.
In his Monday statement, Gardner said the United States is not pressuring China enough, including by sanctioning those "enabling" the North's nuclear program.
As for China, it's taken a tougher stance on North Korea lately but is now more focused on its massive Belt And Road investment in global trading infrastructure.
The White House in a statement said the "latest provocation" shows a need for all countries to implement stronger sanctions against North Korea, and singled out Russian Federation.
U.S. President Donald Trump's administration has called North Korean ballistic and nuclear efforts unacceptable, but he has swung between threats of military action and offers to talk as it formulates a policy.
North Korea's official Korean- Central News Agency (KCNA) called the missile a "new ground-toground medium long-range strategic ballistic rocket", and said the "Hwasong-12" was "capable of carrying a large, heavy nuclear warhead".
South Korea's Han said Sunday's test was "successful in flight". In a show of force, the United States sent an aircraft carrier strike group, led by the USS Carl Vinson, to waters off the Korean peninsula to conduct drills with South Korea and Japan. U.S. Disarmament Ambassador Robert Wood said on Tuesday China's leverage was key and it could do more.