Prime ministership of Mir-Hossein Mousavi secret negotiations and dealing with USA on helping them free the American hostages in Lebanon, in return for sale of the American weapons and spare-parts that Iran's army badly needed for Iran–Iraq War. Shortly after the end of Iran–Iraq War on 20 August 1988, Ruhollah Khomeini died, and Ali Khamenei was elected as the new Supreme Leader by the Assembly of Experts. Following his death, Mousavi and his fellow left-wingers lost their main source of support within the establishment. During the parliament hearing on post-war reconstruction plans, Mousavi had heated arguments with Ali Akbar Hashemi Rafsanjani, the speaker of Iran's
Hossein Shariatmadari Mir Hossein Mousavi was trying to "escape punishment for murdering innocent people, holding riots, cooperating with foreigners and acting as America's fifth column inside the country" and called for Mousavi and former reformist President Mohammad Khatami to be tried in court for "horrible crimes and treason." In 2009, during the first contested presidential elections, Shariatmadari was announced that Mohammad Khatami would risk the same fate of Benazir Bhutto if he was elected. After the elections, alongside the Green Party protests, Shariatmadari accused Mir Hossein Mousavi of being a fifth column of the US and causing the deaths of many people.