Iran has overplayed its hand and now realizes it has made itself an explicit US nuclear target. It has nothing in its defense umbrella right now to deter a major conventional attack, much less a sophisticated strike. Khamenei is a more cautious man than the cartoon Ahmedinejad. Obama's nuclear posture announcement surprised Khamenei and those around him. If you analyze this as a strategic game, nuclear pursuit just made Iran more vulnerable. If it tests a nuclear device, it now must weigh the possibility of nuclear retaliation from America if it responds to a pre-emotive strike from Israel.
Austria bans new admissions to overcrowded migrant center (AP)
from the article: U.S. Defense Secretary: A nuclear Iran is not inevitable