A top Pentagon official said Tuesday it’s unclear why North Korea did not take provocation action such as a missile test after warning the United States about a “Christmas gift” last year.

“Predicting North Korea’s future behavior is always hazardous,” Undersecretary of Defense for policy John Rood told the House Armed Services Committee on Tuesday. “We don’t know fully the reasons why the North Koreans did not engage in more provocative behavior, which they seemed to be hinting they were planning to do in December.”

Pyongyang kept the world on edge during the holiday season after ominously warning that it was up to the United States what kind of “Christmas gift” it would receive.

U.S. officials said at the time they believed the gift could be a long-range missile test, which North Korea has not conducted since it began nuclear negotiations with President Trump.

North Korea never fired a missile in late December or early January. But leader Kim Jong Un did say on New Year’s Day that Pyongyang no longer felt bound by its self-imposed moratorium on long-range missile and nuclear tests, vowing the world would see a new strategic weapon “in the near future.”

Still, Kim did not shut the door to further negotiations with the United States.

Trump has touted the moratorium as a sign of success in his negotiations with Kim, though talks have stalled since a February 2019 summit ended without a denuclearization deal.

And though North Korea hasn’t fired a long-range missile in more than two years, it conducted more than a dozen short-range missile tests last year.

On Tuesday, Rood said the short-range tests were “clearly a message” from North Korea, “as well as a developmental activity.”

Rood added “we could very well see” more missile tests “or other activities” from North Korea, but added that’s “very speculative at this stage.”

“We’re watching very carefully what they’re doing,” he said. “Our message to them has been that obviously that we would regard those things as provocative activities.”

Rood said the U.S. message has also been that getting back to the negotiating table “would be more constructive and productive,” but added “certainly we’ve got to be alert to the possibility that we could see the North conduct those type of tests.”