Former President Jimmy Carter criticized Hillary Clinton this week by saying she "took very little action" to achieve peace during her tenure at the State Department.

Carter told Time Magazine that things only got better when John Kerry took over after President Obama won reelection in 2012.

"I think [his efforts] are notable, and I have a great admiration for him," Carter said about Kerry. "I stay in touch with him fairly often by email. I send him messages and tell him what my thoughts might be, and he has responded very graciously. He has had a very difficult time operating pretty much on his own."

"I know from experience that the best way to have the United States be a mediator is for the president himself to be deeply involved. In this occasion, when Secretary Clinton was Secretary of State, she took very little action to bring about peace," Carter said. "It was only John Kerry's coming into office that reinitiated all these very important and crucial issues."

The 39th president declined to say what he's told Kerry directly, but said that he hopes Kerry doesn't deviate from "long-standing international law" in his dealings with the Middle East and, specifically, Iran.

"I've urged him as he formulates the framework not to deviate from long-standing international law that has always been observed by the United States and by all the Europeans and by the Israelis and the Arab countries," he said.