US-Iran relations may be on the upswing, but a much-anticipated handshake between presidents Obama and Hasan Rouhani never materialized on the sidelines of yesterday's UN meeting, reports NBC News.

The White House had requested a quick meeting between the two leaders, but Iran balked because it was "too complicated for Iranians to do at this point," explains a UN official in a report from the Guardian.

That might mean that the meeting didn't get the green light from Iran's supreme leader back home, Ayatollah Ali Khamenei. (The New York Times today profiles the "enigmatic and cunning man," who is truly calling the shots in Tehran.)

The lack of a presidential get-together means that a Thursday meeting between John Kerry and his counterpart from Iran will be the highest-level encounter. Rouhani addresses the General Assembly later today, and President Obama had positive things to say about him in his own address earlier.