"Everybody's got surprises for me ... I handle them as they come along," he said, adding that the North Korea might send him "a beautiful vase" instead of a missile test.

N.Korea's Vice Foreign Minister Ri Thae Song warned in early December that Washington would soon need to decide what kind of "Christmas gift" it will receive from Pyongyang.

Pyongyang had set its deadline for the denuclearisation negotiations at the end of this year, and it also carried out two "important tests" at its Sohae Satellite Launching Ground on December 7 and 13.

The denuclearisation negotiation between Washington and Pyongyang has lost momentum since the impasse of the Hanoi Summit in late February and the unproductive working-level talks in Stockholm in October.