In international relations and arms control, strategic ambiguity is a national policy of not confirming or denying the possession of certain military capabilities. It is most common in the context of nuclear weapons, but certainly has been used with respect to other capabilities.
The term is most commonly used regarding Israeli nuclear weapons. It has been used for the U.S. policy of not confirming or denying the presence of nuclear weapons aboard United States Navy surface warships, until a declaration was made that they would no longer carry them. South Africa only revealed its nuclear capability after it had voluntarily disarmed. North Korea long suggested it had some weapons, until it chose to conduct an actual test.
Intelligence collection methods used for National Technical Means of Verification may well dismiss, to other governments, the ambiguity if they can confirm the presence of weapons. It is much more difficult, of course, to confirm their absence, although high confidence that certain development or manufacturing facilities cannot be found is suggestive. There also will be truly ambiguous situations, such as the VELA Incident.
Still, even a government that confirms the weapons may not make the information public for diplomatic reasons. If disarmament is its goal, it may believe that this is better done outside the public eye. It also could be advantageous to the witting nation to allow the other country to maintain ambiguity.