Well, president Obama's new nuclear strategy removes that deterrence.

CENTERFORSECURITYPOLICY: Center For Security Policy

One such challenge was whether the United States, with a military strategy based on credible nuclear deterrence, could maintain a highly reliable stockpile of nuclear weapons indefinitely without testing.

CENTERFORSECURITYPOLICY: Center for Security Policy | Fumble on the Test Ban Treaty By Richard Burt The Washington Post, 18 October 1999

It was the enduring need for deterrence that forced the Obama Administration to confront a paradox of nuclear strategy.

FORBES: Nuclear Paradox: Shrinking U.S. Arsenal Requires Huge New Expenditures