The new action, approved in an executive order, targets Iran's currency, the rial, by sanctioning foreign financial institutions that "knowingly conduct or facilitate significant transactions for the purchase or sale of the Iranian rial, or that maintain significant accounts outside Iran denominated in the Iranian rial," press secretary Jay Carney said in a statement.
In the statement, the press secretary said the rial has lost half its value since early 2012 because of U.S. sanctions, but Monday's action was the first time trade in the rial was directly affected.
The executive order also authorizes imposition of more sanctions on individuals who provide material support to Iranian individuals and others included on the list of Specially Designated Nationals and Blocked Persons maintained by the Treasury Department, the statement said.
The executive order also implements and builds upon certain sanctions included as part of the National Defense Authorization Act for 2013.
Iran's automotive sector also is subject to the new round of sanctions.