"The unauthorised test was not connected to any emergency, threat or warning", Guam's Homeland Security Office said in a statement, adding it had worked with the radio stations to "ensure human error will not occur again".
Meanwhile, Ukraine is denying claims that it supplied weapons technology to North Korea, saying its state-owned factory Yuzhmash hasn't created military grade ballistic missiles since the fall of the Soviet Union.
Japan's defence chief and foreign minister will meet their US counterparts on Thursday to reaffirm Washington's commitment to defending Japan, including the use of its nuclear deterrent, as threats from North Korea intensify.
Experts call it a message of confidence aimed at the the U.S., as well as evidence that Pyongyang has been studying the flight path closely.
The top US intelligence official said on Sunday he would not be surprised if North Korea tested another missile, given that it had two tests in July, amid rising tensions between the two nations.
Deadly Barcelona Van Terror Attack Josep Lago AFP Getty Images
He added the US military is prepared to take out any missiles heading toward its territory.
Meanwhile, North Korea says that the issue of Americans detained in the country "is not an object to discuss" in view of current tensions with the United States.
"Military action on the Korean Peninsula can only be decided by South Korea and no one else can decide to take military action without the consent of South Korea", Moon said in a speech to commemorate the anniversary of the nation's liberation from Japanese military rule in 1945.
Steve Ganyard, an ABC News aviation contributor and retired Marine Corps colonel, agreed: "Kim Jong Un is a rational man, so the whole goal is regime survival". They have the land border with North Korea.
Mattis and Tillerson also credited UN efforts and said the United States was willing to negotiate with North Korea, but said Pyongyang should indicate a desire to show good faith by halting weapons and nuclear tests.
Experts contacted by Business Insider found the prospect of North Korea carrying out its plan unlikely.