And the White House noticed.
A senior administration official confirmed that White House staff saw Rouhani's first tweet about the call when it posted to Twitter just before Obama told reporters in a statement in the briefing room. Rouhani quickly erased the tweet, but he later resumed posting about the phone call on the social network, where he has more than 65,000 followers on his English account.
Rouhani's tweets "certainly reflected the tone of the conversation between the two leaders," the White House official said, "and we'll continue to watch his Twitter feed."
Rouhani has tweeted more than 1,800 times since setting up the account, which the official called a "welcome development" and a "positive and constructive step" as the more moderate Iranian leader reaches out to the United States and the rest of the world.
But the White House official emphasized that the administration would like the Rouhani regime to allow social media access to ordinary Iranians.
"What we've noticed is Iran, like many other countries, has a youthful population that very much enjoys getting on and expressing their views through social media," the official said. "So we believe that that's a positive means for not just free expression but communication."