North Korean leader Kim Jong-un, center, visits the Kumsusan Palace of the Sun where his late father's body is enshrined to commemorate the eighth anniversary of his father's death in Pyongyang, the Korean Central News Agency reported Tuesday. Yonhap

U.S. President Donald Trump said Monday that he would be disappointed if something was "in the works" in North Korea and that the United States is watching the regime closely.

Tensions between the two nations have escalated ahead of a year-end deadline set by the North, after which the regime has hinted at resuming nuclear or long-range missile tests.

Trump's comments come after North Korea on Friday carried out a second presumed engine test in less than a week at its Sohae satellite launching facility.

"I'd be disappointed if something would be in the works, and if it is, we'll take care of it," Trump told reporters at a meeting with governors at the White House. "We're watching it very closely."