The United States blacklisted Iran’s state broadcasting authority, Internet-policing agencies and a major electronics producer on Wednesday, an action that widened the American sanctions effort to pressure the Iranian government over not only its disputed nuclear program but also over the stifling of domestic dissent and access to information.

A statement by the Treasury Department also announced the formal start of tightened restrictions, under a law passed last year, meant to severely inhibit Iran’s already weakened ability to repatriate earnings from the sale of oil, its most important export.

David S. Cohen, the Treasury undersecretary for terrorism and financial intelligence, who oversees the sanctions effort, said the actions were meant to “intensify the economic pressure against the Iranian regime.”

He said, “We will also target those in Iran who are responsible for human rights abuses, especially those who deny the Iranian people their basic freedoms of expression, assembly and speech.”