SEOUL, South Korea — North Korea today boasted of a successful weekend launch of a new type of “medium long-range” ballistic rocket that can carry a nuclear warhead. Outsiders also saw a significant technological jump, with the test-fire apparently flying higher and for a longer time period than any other such previous missile.

Amid condemnation in Seoul, Tokyo, Washington and Moscow, a jubilant North Korean leader Kim Jong Un promised more nuclear and missile tests and warned that his country’s weapons could strike the U.S. mainland and Pacific holdings.

North Korean propaganda must be considered with wariness — Pyongyang has threatened for decades to reduce Seoul to a “sea of fire,” for instance — but today’s claim, if confirmed, would mark another big advance toward the North’s goal of fielding a nuclear-tipped missile capable of reaching the U.S. mainland. Some experts, including officials in Tokyo, estimate that Sunday’s launch successfully tested a new type of missile, potentially the longest in North Korea’s arsenal.

The test is also an immediate challenge to South Korea’s new president, Moon Jae-in, a liberal elected last week who expressed a desire to reach out to North Korea. Pyongyang’s aggressive push to boost its weapons program also makes it one of the Trump administration’s most urgent foreign policy worries.