North Korean leader Kim Jong Un celebrated a test of the “perfect weapon system” after his engineers launched what they said was new kind of intermediate-range ballistic missile system capable of carrying “a large-size heavy nuclear warhead.”

The missile, launched Sunday morning, appeared to show substantial progress toward developing an intercontinental ballistic missile that can reach the mainland United States, American rocket scientists said.

“North Korea’s latest successful missile test represents a level of performance never before seen from a North Korean missile,” said John Schilling, an aerospace engineer who specializes in rockets. This means North Korea may be only one year, rather than the expected five, from having an ICBM, he said.

The latest launch was widely condemned, with the White House calling North Korea a “flagrant menace” and urging allies to impose stronger sanctions. South Korea and Japan also condemned the launch.