Adam Mount, a senior fellow at the Federation of American Scientists in Washington, said North Korea had previously tested only a small number of SLBMs, despite claiming for a number of years to have the capacity.

Mount said North Korea viewed SLBMs as another method to get past the missile defenses of the United States and its allies, specifically South Korea and Japan. "They're concerned our missile defenses nullify their deterrent capabilities," he said.

But Mount added SLBMs are only as good as the vessels that carry them, and the US military was more than a match for North Korea's noisy submarines.

"The weak link in their submarine missile program is the submarines, and that is an enormous technical challenge for the North Koreans," he said, adding Pyongyang's vessels were so outmatched, the SLBMs were effectively a "redundant capability."

Mixed signals on Korean Peninsula

North Korea's Tuesday missile test came after weeks of seesawing tensions on the Korean Peninsula, which saw growing cooperation between Pyongyang and Seoul at the same time as rising military brinksmanship.

On October 4, Pyongyang agreed to reopen official communications with Seoul for the first time in months. South and North Korea spoke on a joint-communication line on Tuesday shortly before the missile test, a South Korean Unification Ministry official said, but the North did not discuss the launch during the call.

In a statement Tuesday, the US Indo-Pacific Command said it was aware of North Korea's latest missile launch and would work closely with regional allies to monitor the situation.

"The United States condemns these actions and calls on the DPRK to refrain from any further destabilizing acts," the statement said, referring to North Korea by its official name. "The US commitment to the defense of (South Korea) and Japan, remains ironclad."