1105 GMT July 17, 2018
Es'haq Jahangiri made the announcement late Monday following an emergency meeting of the government's economic taskforce headed by President Hassan Rouhani, reported Press TV.
The first vice president said that the dollar exchange rate would be 42,000 rials in both markets, and for all types of activities.
He added that the US dollar sold at any other price would be considered contraband.
On Sunday, Iran's national currency the rial plunged above six percent against the US dollar in the free market.
Commercial bankers earlier linked the rial's slide partly to seasonal demand for US dollars, which rises around the end of the Iranian year (in March) when many Iranians travel abroad.