On the Twitter account, USA darFarsi, the department told Iranians, "We want to join in your conversation."
The second and third tweets were more pointed. The State Department accused Iran's government of illegalizing dissent while praising Egyptian protesters for the same activities.
The U.S. then called on Iran "to allow people to enjoy same universal rights to peacefully assemble, demonstrate as in Cairo."
The Farsi Twitter account had 60 followers within two hours of its launch.
Last week, the State Department launched an Arabic Twitter feed in an effort to communicate with the Egyptian protesters who eventually brought about the resignation of President Hosni Mubarak.