Senator Marco Rubio, Republican of Florida, said he would "absolutely" send another letter to Iran.
"I would send another one tomorrow. I think the risk of a nuclear Iran is so great that we need to do everything possible to keep us from finding us in a situation where we are going to have a nuclear Iran," Rubio told NBC News after he spoke at a fire fighters conference in Washington, D.C.
Forty-seven Republican senators sent a letter to Iran saying they would work to unravel any deal reached between the United States and Iran over its nuclear program.
Sen. Lindsey Graham of South Carolina, who has also indicated a possible run for the White House, spoke to the fire fighters about the danger of the negotiations. "There are no moderates running Iran," he said.
The letter has resulted in a domestic political firestorm that could have international consequences.
Vice President Joe Biden said the letter is "expressly designed to undercut a sitting President in the midst of sensitive international negotiations, is beneath the dignity of an institution I revere."
The lead author of the letter, Freshman Sen. Tom Cotton of Arkansas, said on MSNBC's Morning Joe defended the letter saying "we simply wanted to state clearly to Iran's leaders if we don't approve a nuclear deal, then we won't accept it, and that Iran 's leaders can only be certain that any deal will be lasting if Congress approves it."
At the same conference, Rep. Peter King, R-New York, said he didn't know if he would have signed the letter if he were in the Senate. "Even though I don't trust the president on this, quit frankly, I don't know if I'd go public with a foreign government."
- Leigh Ann Caldwell, Luke Russert and Alex Moe