But the president said in an interview that he was carving out an exception for “outliers like Iran and North Korea” that have violated or renounced the main treaty to halt nuclear proliferation.
Discussing his approach to nuclear security the day before formally releasing his new strategy, Mr. Obama described his policy as part of a broader effort to edge the world toward making nuclear weapons obsolete, and to create incentives for countries to give up any nuclear ambitions. To set an example, the new strategy renounces the development of any new nuclear weapons, overruling the initial position of his own defense secretary.
Mr. Obama’s strategy is a sharp shift from those of his predecessors and seeks to revamp the nation’s nuclear posture for a new age in which rogue states and terrorist organizations are greater threats than traditional powers like Russia and China.
It eliminates much of the ambiguity that has deliberately existed in American nuclear policy since the opening days of the cold war. For the first time, the United States is explicitly committing not to use nuclear weapons against nonnuclear states that are in compliance with the Nuclear Nonproliferation Treaty, even if they attacked the United States with biological or chemical weapons or launched a crippling cyberattack.
Those threats, Mr. Obama argued, could be deterred with “a series of graded options,” a combination of old and new conventional weapons. “I’m going to preserve all the tools that are necessary in order to make sure that the American people are safe and secure,” he said in the interview in the Oval Office.
White House officials said the new strategy would include the option of reconsidering the use of nuclear retaliation against a biological attack, if the development of such weapons reached a level that made the United States vulnerable to a devastating strike.
Mr. Obama’s new strategy is bound to be controversial, both among conservatives who have warned against diluting the United States’ most potent deterrent and among liberals who were hoping for a blanket statement that the country would never be the first to use nuclear weapons.
Mr. Obama argued for a slower course, saying, “We are going to want to make sure that we can continue to move towards less emphasis on nuclear weapons,” and, he added, to “make sure that our conventional weapons capability is an effective deterrent in all but the most extreme circumstances.”
The release of the new strategy, known as the Nuclear Posture Review, opens an intensive nine days of nuclear diplomacy geared toward reducing weapons. Mr. Obama plans to fly to Prague to sign a new arms-control agreement with Russia on Thursday and then next week will host 47 world leaders in Washington for a summit meeting on nuclear security.