Russia appears more willing to deploy nuclear weapons today than during the Cold War, U.S. Defense Secretary Asht Carter has warned.

Speaking at Minot Air Force Base in North Dakota on September 26, he accused Moscow of "nuclear saber-rattling" as it conducts more nuclear exercises and engages in more strident nuclear rhetoric.

"It is a sobering fact that the most likely use of nuclear weapons today is not the massive 'nuclear exchange' of the classic Cold War-type, but rather the unwise resort to smaller but still unprecedentedly terrible attacks, for example by Russia or North Korea," he said.

He also expressed concern over Russia's push to overhaul its atomic weapons systems even as he announced that the United States would push ahead with building a new generation of nuclear weapons at a cost of more than $100 billion.

Russia's nuclear build-up "raises serious questions about its leaders' commitment to strategic stability, their regard for long-established accords against using nuclear weapons, and whether they respect the profound caution that Cold War-era leaders showed with respect to brandishing nuclear weapons," Carter said.

Based on reporting by AP and AFP