Former U.S. Secretary of State John Kerry told CNBC on Thursday that he has not sought to influence Iranian foreign policy since leaving the State Department.

Speaking to CNBC's Hadley Gamble in Normandy, France on Thursday, Kerry was asked to respond to recent criticism from Secretary of State Mike Pompeo.

Last month, Pompeo described Kerry's reported conversations with his former Iranian counterpart as "inappropriate."

"I haven't talked to the Iranians subsequently about any issue. I've only talked with one Iranian once between the decision that was made to pull out," said Kerry, the unsuccessful 2004 Democratic presidential candidate who became the top U.S. diplomat during President Barack Obama's second term.

"I saw the foreign minister briefly for a few minutes at the Munich Security Conference. But, I have not said a word subsequently to what they ought to do or not do. It's not my business."

When asked to clarify whether there had been any back-channeling, Kerry replied: "No, I haven't had any back-channel on that issue since the decision was made to move out. And before that it was not a back-channel."

Kerry said it has been common practice for previous secretaries of state, U.S. senators and many others to continue having public discussions with people "as a matter of being well informed."