North Korea's Musudan intermediate-range ballistic missile, believed to be capable of reaching the US territory of Guam, could become operational sometime next year, a top US missile expert said warned Monday, noting that last week's launch of the missile, albeit a failure, could be part of a field test.

The North test-fired a Musudan missile on Saturday, but the missile exploded shortly after take-off. It was believed to be the seventh test of the missile this year, coming after June's successful launch in which the missile entered space and re-entered Earth's atmosphere.

"They are continuing with an aggressive test schedule that involves, at least this time, demonstrating new operational capabilities. That increases the probability of individual tests failing, but it means they will learn more with each test even if it does result in failure," John Schilling, a top aerospace engineer with expertise in the North's missile programs, said.

"If they continue at this rate, the Musudan intermediate-range ballistic missile could enter operational service sometime next year -- much sooner than had previously been expected," he said in an article to 38 North, a website focused on North Korea analysis.

The expert said it's noteworthy that the North conducted the latest test from the northwestern city of Kusong, away from the usual test site on the opposite side of the country. That could be an attempt to allow the missile to fly its fullest range without violating Japan's airspace, he said.

In June's test, which was conducted from the usual site on the east coast, the North launched the missile at a lofted angle in order to avoid violating Japan's airspace. Though the missile landed in waters 400 kilometers away, the test was considered a success as it reached space and re-entered the atmosphere.

"Moving to a roadside near Kusong is like taking the training wheels off the bicycle, seeing if you really have mastered something new," Schilling said. "From the west coast, launching south, a North Korean missile could fly 3,000 kilometers or more before splashing down in the Philippine Sea."

The expert also said that last week's test shows Kusong could become the Musudan's operational basing area.

"There is a saying in our military that amateurs practice until they get it right, but professionals practice until they can't get it wrong. The North Koreans have just shown that they can still get it wrong, but they are still practicing," he said.

"Seven launches in seven months -- a rate greater than most US strategic missile programs. After a decade of keeping it on the back burner, the North Koreans are clearly committed to the Musudan. Another seven months of training and practice could bring them to a real initial operational capability," he said. (Yonhap)