North Korean dictator Kim Jong Un has promised a "Christmas gift" to the US if sanctions aren't lifted.
According to CNN, the Trump Administration interprets the statement to mean a weapons test.
No such tests have been detected from North Korea since Christmas.
However, officials have remained watchful.
National security adviser Robert O'Brien said on ABC's 'This Week that if tests resume, the US will take action.
If Kim Jong Un takes that approach, we'll be extraordinarily disappointed and we'll express that disappointment.
Robert O'Brien National Security Adviser, Trump administration It's unknown, however, what the threshold of North Korean action would be to generate a response from the US.
North Korea has fired several short-range missiles in recent months without any US military response.