The Treasury Department said it was working to restrict Iran's ability to use oil revenue that may be held in foreign banks.
"In addition to effectively 'locking up' Iranian oil revenue overseas, this provision sharply restricts Iran's use of this revenue for bilateral trade and severely limits Iran's ability to move funds across jurisdictions," the Treasury Department said.
Iran's economy relies in part on oil revenue from foreign sales. The national currency, the rial, collapsed last year under sanctions pressure.
Countries such as the United States say Iran may be using oil revenue to fund a nuclear program, which Tehran says is for peaceful purposes.
"So long as Iran continues to fail to address the concerns of the international community about its nuclear program, the U.S. will impose tighter sanctions and intensify the economic pressure against the Iranian regime," Treasury Undersecretary for Terrorism and Financial Intelligence David Cohen said.
Some of Iran's consumers received relief from previous sanctions if they could show the U.S. government they reduced their reliance on Iranian crude oil.
New U.S. sanctions target Iranian broadcasters for alleged human rights and censorship violations.