Obama to Iran: a new start
Iran's supreme leader Ayatollah Ali Khamenei has demanded concrete policy changes from the US as the price for new relations between the two states.
Speaking in the holy city of Mashhad, Ayatollah Khamenei said: "If you change your attitude, we will change our attitude."
Click below to hear former US ambassador William Luers's analysis of President Obama's video message to Iran.
(broadcast on The World Tonight, BBC Radio 4, 20 March 2009)