President Barack Obama, in a message to Iran's people and leaders on Thursday, said this year represented the "best opportunity in decades" to pursue a different relationship between their two countries.

Obama said nuclear talks with Iran had made progress but that gaps remained.

"This moment may not come again soon," Obama said in his message celebrating Nowruz, the Iranian New Year. "I believe that our nations have an historic opportunity to resolve this issue peacefully — an opportunity we should not miss"