At 3:35 p.m. ET, Iranian President Hassan Rouhani sent out a tweet that marked the most significant progress in U.S.-Iranian relations in more than three decades:

The tweet was quickly deleted — perhaps because Rouhani had inadvertently scooped what would be a huge announcement from U.S. President Barack Obama. Depending on what happens in the months and years to come, Rouhani's tweet has the potential of being a historic announcement.

"Just now, I spoke on the phone with President Rouhani of the Islamic Republic of Iran," Obama said at 3:42 p.m. ET in a statement from the White House briefing room. It was the first time that U.S. and Iranian leaders had spoken since the 1979 Iranian revolution.

"The two of us discussed our ongoing efforts to reach an agreement over Iran’s nuclear program. I reiterated to President Rouhani what I said in New York — 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 on the phone with Rouhani. Twitter/@PeteSouza The call marked more progress in the thawing of icy relations between the two countries, which has come on the heels of repeated conciliatory statements from Rouhani since he assumed office in early August. Earlier this week, Obama spoke at the United Nations and said that the U.S. would pursue a path of diplomacy with Iran.

In a conference call with reporters, a senior administration official said that Iran's government initiated the phone call following a week of progress at the U.N. that included a high-level meeting between U.S. Secretary of State John Kerry and Iranian Foreign Minister Javad Zarif.

The call took place around 2:30 p.m. ET for 15 minutes, the official said. Obama made the call while Rouhani was in a car to the airport.

The administration official said that Congress and Israel's government were notified of the call between the two leaders, and that Israel will be kept updated of progress in negotiations.

"This is something we have an obligation to test," the administration official said of diplomatic relations with Iran.

The official also said that the White House was aware of Rouhani's Twitter account. Though it is not verified, the White House seemed to confirm that the account is authentic. The official said it provided an accurate readout of the leaders' call.

"We did watch President Rouhani's Twitter feed," the official said. "Frankly, we've watched him use social media to communicate over the last several weeks." The official said it was a "welcome development."

The two leaders spoke through interpreters. But at the end of the call, they parted by offering "good byes" in their respective languages.

"Have a nice day!" Rouhani said in English.

"Thank you. Khodahafez," Obama responded, the Farsi parting phrase that means "good bye."



