A new report reveals how the Obama administration has upgraded the U.S. nuclear arsenal to create smaller, more precise nuclear bombs. The New York Times reports that despite his advocacy for a "nuclear-free world," President Obama’s administration has potentially increased the likelihood of a future president deploying a nuclear weapon by creating more precise warheads whose explosive force can be dialed up or down. A former top nuclear strategist for Obama, General James Cartwright, acknowledged "what going smaller does is to make the weapon more thinkable." The B61 bomb is part of a fleet of new warhead types planned under an effort that will cost up to $1 trillion over three decades. Russia has called U.S. tests of the missile "irresponsible" and "openly provocative." The U.S. is the only country ever to use a nuclear weapon in war.