The spokesman, whose comments were reported by Fars news agency, condemned Saudi Arabia, the world's biggest oil exporter, and Bahrain for welcoming US sanctions on Tehran.
Mousavi called US sanctions illegal, cruel and driven by bullying and said "We are hopeful that those buyers of Iranian oil who stood against this unilateral move in their comments, also take action."
China, Iran's largest crude oil customer, formally complained this week to the United States over its decision to end waivers on sanctions on Iranian oil imports.
Saudi Energy Minister Khalid al-Falih said on Thursday that China had "not yet" asked for more oil after the United States decided to end its waivers that had allowed Beijing to keep buying from Tehran.