According to the Wall Street Journal, the United States Attorney for the Southern District of New York has filed a forfeiture proceeding against 650 Fifth Avenue in New York.
In its press release: United States files civil forfeiture action against ASSA corporation’s interest in Manhattan office tower (.pdf), the DOJ claims that a 40% interest in the building is held by the ASSA Corporation which is acting as a front for Bank Melli. The Government of Iran controls Bank Melli and ownership is considered an export under the Iraninan Transaction Regulations (Title 31 CFR, part 560)