Senator Joni Ernst.

Senator Joni Ernst.

Both of Iowa’s Senators are among the 47 Republicans who signed a letter to Iran’s leaders, warning that congress would seek to weigh in on any deal Iran might reach with the U.S. over nuclear weapons. Senator Joni Ernst today said she doesn’t believe Iran wants to use nuclear material for “peaceful purposes” and that’s one reason why she signed the letter.

“Any agreement that is made by our president is not binding,” Ernst said. “…We could have another president that enters the office in a few years and decides he does not want to follow what was agreed to by President Obama.”

The letter has caused a firestorm in Washington, with Democrats accusing the Republicans of trying to undermine the negotiations. Vice President Biden issued a statement saying the letter was “beneath the dignity” of the U.S. Senate. Senator Chuck Grassley on Tuesday said he doesn’t know why the letter has become controversial.

“We want the people of Iran and the government of Iran to understand that an agreement between our president and their president…that that’s just an agreement and a new president can come along and that he doesn’t have to abide by that agreement,” Grassley said.

The letter makes it clear congress is an “independent branch” of the U.S. government, according to Grassley.

“We don’t have to do just what the president tells us to do,” Grassley said.

Senator Chuck Grassley

Senator Chuck Grassley

Grassley contends any deal with Iran over its nuclear ambitions should be a formal treaty rather than just an agreement and a treaty would be subject to an up or down vote in congress.

“Now there are agreements that are legitimate, but in this particular case it ought to be treated as a treaty,” Grassley said. “And we don’t think the president’s going to do that.”

Some critics have gone so far as to call the GOP senators who signed the letter traitors. Ernst, who was asked to respond to that criticism this morning, said the letter merely makes it clear to Iran’s leaders that they are “dealing only” with the executive branch of the U.S. government.

“I don’t think we are undermining the president,” Ernst said. “This was a letter directed to Iranian officials to just basically state that what agreements are reached between the president and the Iranian government is not necessarily something that is likely to be followed in the future by future a congress or future presidents.”

According to Ernst, any “long-standing agreement” between Iran and the U.S. must be approved by congress.

“And we cannot afford to stand by and watch as a deal is negotiated that paves the way for Iran to obtain nuclear weapons,” Ernst said.

Ernst and Grassley made their comments during telephone news conferences with Iowa reporters.

Radio Iowa