Cuba has shown no desire to rejoin. Socialist states like Venezuela and Nicaragua say they want to form an association that excludes the US.
President Mahmoud Ahmadinejad faced off against one of his three opponents, Mir Hossein Mousavi, Wednesday night in the second of six debates leading up to June 12 elections.
The president addressed extremism, the Israeli-Palestinian conflict, women's rights, and nuclear proliferation, among other topics.
Many welcomed the US president's conciliatory tone and references to Islamic history. Skeptics pointed to the price Pakistan pays for ongoing US involvement in Afghanistan.
'The absence in his speech of any bellicose threats to Iran stands in stark contrast to his predecessor,' says a Muslim politician in Birmingham.
Obama criticized Holocaust deniers. But Ayatollah Khamenei praised US effort at a "new image."