"Today's action makes it clear that we will expose any financial institution, no matter where they are located, that allows the increasingly desperate Iranian regime to retain access to the international financial system," Obama said in the statement released by the White House.
Mark Dubowitz, executive director of the Foundation for Defense of Democracies in Washington, said while the sanctions are "important measures," the U.S. approach "still involves a game of Whac-A-Mole because the administration, in particular Treasury, still has to chase down" each new Iranian move to circumvent sanctions.
"I don't think any of these sanctions so far have created enough fear" to get Iran to stop pursuing a nuclear weapons program, Dubowitz said. An alternative is to "blacklist automatically any interaction with Iran's energy sector" except for those permitted under U.S. exemptions.
"Clearly, there's a political angle to this," Dubowitz said. "The administration is trying to demonstrate it can be proactive and not just reactive and blunt some of the criticism from Romney and congressional Republicans."
Ben Rhodes, Obama's deputy national security adviser, said the sanctions were being developed prior to Romney's overseas trip and that the timing of the announcement was coincidental.
U.S. sanctions are part of the international economic pressures on Iran to give up suspected efforts to develop nuclear weapons. Iran denies pursuing nuclear weapons ambitions and says its nuclear program is for peaceful energy and medical purposes.