Seoul (CNN) North Korea has tested a "newly developed ultramodern" weapon in an event supervised by leader Kim Jong Un, state media said Friday, amid faltering nuclear disarmament negotiations with the United States.

Very little is known about the weapon or whether it is even new, but the test is the latest sign that Pyongyang is prepared to return to a more militaristic relationship with Washington if talks continue to go poorly.

"He's tiptoeing towards a more aggressive posture in negotiations with the US and he's signaling that he's not going to give way and can simply return to his old practices if (the US) don't change their approach," Josh Pollack, senior research associate at the Middlebury Institute of International Studies at Monterrey, told CNN.

In this undated photo released on Friday by the North Korean government, Kim Jong Un, listens to a military official as he inspects a weapon testing.

North Korea's state news agency KCNA announced the test on Friday morning, providing no details on the location of the event and little information about the weapon itself other than it was "tactical" and had been commissioned "personally" by Kim's father and predecessor, Kim Jong Il.

A South Korean government source with military knowledge told CNN the weapon was likely a piece of long-range artillery "likely to be a multiple rocket launcher."

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