North Korea has moved a missile with “considerable range” to its east coast, South Korea’s defense minister said Thursday.

Kim Kwan-jin quickly dismissed the development as an escalation of the regime’s threats of a nuclear strike on the US, saying that he did not know the reasons behind the missile’s movement, which came hours after the regime’s military warned that it authorized plans to attack targets on the US.

The missile has “considerable range”, Kim said, refuting reports in Japanese media that the missile could be a long-range KN-08 missile capable of hitting the US mainland.

The intermediate-range missile will likely be used for a test-firing drill, Kim told lawmakers at a parliamentary committee meeting.

Intelligence analysts said the missile was believed to be a North Korean missile known as the Musudan, with an estimated range of 3,000 kilometers (1,800 miles), that could reach immediate targets such as Japan and South Korea.

Washington announced that it will hasten the deployment of a missile defense system to the US Pacific territory of Guam to strengthen regional protection against a possible attack, reports The Associated Press.

UN Secretary General Ban Ki-moon warned that if North Korea does not rein in its threats, “any misjudgement, any miscalculations” could lead to an extremely grave outcome.

“Nuclear threat is not a game, it is very serious,” Ban told reporters. “I think they have gone too far in their rhetoric.”