North Korea may be capable of fielding a nuclear-armed missile that could reach U.S. soil, but because it has not tested such a weapon the odds of it being effective are "pretty darn low," the commander of U.S. forces in South Korea said Friday.

In remarks at the Pentagon, Army Gen. Curtis Scaparrotti noted that North Korea claims to have such a missile, although some have questioned whether they have achieved all of the key technological breakthroughs, including manufacturing a nuclear warhead small enough for a long-range missile.

Scaparrotti said it would be imprudent of him to ignore their claims.

"Personally I think that they certainly have had the expertise in the past," Scaparrotti said. "They've had the right connections, and so I believe they have the capability to have miniaturized a device at this point, and they have the technology to potentially actually deliver what they say they have."

He added, "We have not seen it tested. And I don't think as a commander we can afford the luxury of believing perhaps they haven't gotten there."

The missile in question is designated by the U.S. as the KN-08. In January, Director of National Intelligence James Clapper told a congressional hearing that North Korea had taken initial steps toward fielding the KN-08 although it remained untested.

Pressed further on the question of whether North Korea has the capability of making a nuclear warhead small enough to affix to a long-range missile, Scaparrotti said, "I don't know that they do. What I'm saying is, is that I think given their technological capabilities, the time that they been working on this, that they probably have the capabilities to put this together."

He stressed that the North Koreans have not yet tested the KN-08.

"For something that's that complex, without it being tested, the probability of it being effective is pretty darn low," he said.