New York__ President Obama spoke by phone with Iran's President Hassan Rouhani Friday, officials from both countries said, another remarkable gesture in a week in which US and Iranian leaders moved tentatively to test opportunities to forge more direct contacts in and out of the public spotlight.

"Just now, I spoke on the phone with President Rouhani of the Islamic Republic of Iran," Obama said in a hastily arranged press conference Friday. "The two of us discussed our ongoing efforts to reach an agreement over Iran’s nuclear program....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."

The 15-minute phone call--the first between presidents of the two countries since 1979--was initiated by Obama at 2:30pm Friday as Rouhani was wrapping up his four day trip to New York, after the Iranians reached out Friday to express interest in a call, US and Iranian officials said. It came a day after Secretary of State John Kerry and Iranian Foreign Minister Mohammad Javad Zarif also made history, by meeting one on one Thursday for half an hour, on the sidelines of six party nuclear talks.

Obama, in the call, congratulated Rouhani on his election, and urged that the two leaders seize the opportunity for a nuclear deal, a senior US administration official said Friday. A "breakthrough on the nuclear issue could open the door to a [more constructive] relationship between the US and Iran," the US official summarized.