US President Barack Obama issued a vigorous defense of his policy of diplomatic engagement with historic adversaries such as Cuba and Iran, saying the negotiations with Iran have resulted in demonstrable restraints on Iran’s nuclear program.

“You look at an example like Iran, over the last year-and-a-half, since we began negotiations with them, that's probably the first year-and-a-half in which Iran has not advanced its nuclear program in the last decade,” Obama said in an interview with CNN’s Candy Crowley Dec. 21.

“We know that,” Obama continued. “That’s not just verified by the United Nations and the IAEA [International Atomic Energy Agency] and ourselves. Even critics of our policy, like the [Benjamin] Netanyahu government in Israel, their intelligence folks have acknowledged that, in fact, Iran has not made progress.”

Obama said his announcement last week that he is authorizing normalization of relations with Cuba shows he is seizing opportunities to change course and thaw relations with historic adversaries.

“Cuba offers us an example of an opportunity to try something different,” Obama told CNN. “For 50 years, we have tried to see if we can overthrow the regime through isolation. It hasn't worked. If we engage, we have the opportunity to influence the course of events at a time when there's going to be some generational change in that country.”