President Obama says he has had a phone conversation with new Iranian President Hassan Rouhani.

Speaking at the White House, the President cited a thaw in U.S.-Iranian relations and expressed optimism about resolving a longstanding dispute over those programs. He said it's the first direct discussion between the presidents of the U.S. and Iran since 1979.

"While there will surely be important obstacles to moving forward, and success is by no means guaranteed, I believe we can reach a comprehensive solution," Obama said.

Iranian and U.N. officials have been meeting to continue talks on how to investigate suspicions that Iran has worked secretly on nuclear weapons.