U.S. President Barack Obama has told Iranians this year represented the "best opportunity in decades" to pursue a different relationship between their two countries.
In his message celebrating Norouz, the Iranian New Year, Obama said nuclear talks with Iran had made progress but that gaps remained.
"I believe that our nations have an historic opportunity to resolve this issue peacefully -an opportunity we should not miss," Obama said.
Obama said Iran has kept its commitments under an interim nuclear deal. But he said coming days and weeks are critical.
Obama said there's a way for Iran to assure the world it doesn't want nuclear weapons. He said that path would lead to greater opportunities for Iranians.
But Obama says if Iran's leaders don't choose that path, Iranians will remain isolated and deprived of global opportunities.
Iran and six world powers are negotiating an agreement to curb some of Iran's nuclear work in return for sanctions relief.
Tehran denies charges it is secretly developing a nuclear weapons program.
Based on reporting by AP and Reuters