US President Barack Obama says a revamped American nuclear strategy will narrow the conditions in which nuclear weapons would be used, even in self-defence.
In an interview in The New York Times newspaper, Mr Obama said exceptions would be carved out for he called "outliers" like Iran and North Korea that have either violated or renounced the Nuclear Proliferation Treaty.
Mr Obama will on Monday unveil a fresh US nuclear strategy.
He has signaled it will call for reducing the size and role of America's stockpile of atomic weapons.
