And Mark Dubowitz of the Foundation for Defense of Democracies, who has consulted with the U.S. government on sanctions, said the audience of the letter was more the American people than the Iranian leadership.
"I don't think anyone thinks that the supreme leader of Iran is going to decide not to do a nuclear deal because Tom Cotton or 46 other senators sent a letter," he said.
"I think that the target of the letter was not Iran's supreme leader but President Obama. The letter is designed to make the public case that any arms control agreement with Iran has to be ratified by the U.S. Senate."
Dubowitz said that the letter was designed to bolster the case for a bipartisan bill framed by Senate Foreign Relations Committee Chairman Bob Corker and his Democratic counterpart, Sen. Robert Menendez, that would require Obama to submit any Iran deal to Congress within 60 days for a vote.
Dubowitz added that he supported an effective deal with Iran and worried that without congressional backing, hopes of a long-term solution to the Iran nuclear crisis would be dashed.