"We have already warned several times that we will take counteractions for self-defense, including a salvo of missiles into waters near the USA territory of Guam", Pyongyang said in a state-run KCNA report.
The USS Michigan nuclear-powered submarine enters the naval base of Busan, South Korea, on October 13, 2017.
Separately, a small quake was detected early yesterday near the North's nuclear test site, South Korea's weather agency said, but unlike quakes associated with nuclear tests, it did not seem to be man-made.
The nuclear-powered submarine MI arrived at the South Korean port of Busan on Friday.
The former USA leader has visited the isolated state three times in the past on diplomatic missions.
It is unlikely to have any effect on next week's planned major joint-navy drill between Sourth Korea and the U.S.
This week, officials in Washington and Seoul have said that the U.S. and South Korean navies will stage a combined Maritime Counter Special Operation Force (MCSOF) exercise, as well as a drill with U.S. Navy carrier strike groups (CSG), in waters off the east and west coast of South Korea.
North Korean leader Kim Jong Un inspects the long-range strategic ballistic rocket Hwasong-12.
North Korea has launched two missiles over Japan and conducted its sixth nuclear test in recent weeks as it advances quickly toward its goal of developing a nuclear-tipped missile capable of hitting the US mainland. "The U.S. military action hardens our determination that the U.S. should be tamed with fire and lets us take our hand closer to the "trigger" for taking the toughest countermeasure".
"If the USA imperialists and South Korean puppets ignite an aggressive nuclear war against us, it would only advance their own demise", the state-run Korea Central News Agency said in a Friday report.
It remains unclear whether North Korea will lash out with a weapons test during the exercise, as it often has in the past.
"Right now we think the threat is manageable", Kelly told reporters, via a live feed.
But he stipulated there is "great concern" for the citizens of Guam, which features a significant number of USA military installations.