Representatives of the Islamic Union of Iranian Students announced it intended to ensure the website crashed the moment it opened.
Hillary Clinton, the US Secretary of State, announced last week that Washington would launch the online embassy by the end of the year.
It will include information on American education programmes as well as visa requirements to assist Iranians in bypassing government curbs on internet use.
“We will not allow the United States to enter Iran,” said the union secretary, Seyed Ali Mousavi.
