John Kerry
John Kerry Reuters

Former U.S. Secretary of State John Kerry on Sunday ripped President Donald Trump over his decision to leave the 2015 Iranian nuclear deal, claiming the President “doesn't know what he's talking about”.

In an interview with CBS’ “Face the Nation”, Kerry rejected Trump’s comments that the deal is the worst deal he has ever seen.

“[J]ust saying that doesn't make it that. This is the toughest agreement in terms of inspection, accountability, what Iran was required to do, with the greatest visibility for the longest period of time of any nuclear agreement on the planet,” he continued.

“No country has had to do what Iran did in order to live up to this. But to just walk away while Russia, China, France, Germany, and Britain are all trying to keep this agreement in place. Only the United States walked away, only Donald Trump. So I think that experts who understand- the Defense Department - his defense secretary thought he should keep it. The Secretary of State that he got rid of (Rex Tillerson -ed.) thought he should keep it. His intelligence people thought he should keep it,” said Kerry.

Trump withdrew from the accord in May and recently signed an executive order officially reinstating U.S. sanctions against Iran.

Kerry was asked in Sunday’s interview about his efforts to save the deal. The Boston Globe revealed in May that Kerry met with Iranian Foreign Minister Mohammed Javad Zarif, angering Trump who in turn blasted Kerry on Twitter.

The former Secretary of State rejected claims that he was trying to undermine Trump, saying, “I was trying to have the policy of the United States of America which was part of the agreement to continue and common sense to continue. I didn't negotiate. I spoke out, and I will always exercise my right to speak out.”

Kerry said he did not put any stock in Trump’s personal attacks on him, asserting that he almost walked away from the talks with Iran “on two or three other occasions where we thought it was necessary.”

“So he really, unfortunately, and I say this sadly- you know, more often than not he really just doesn't know what he's talking about. He makes things up, and he's making that up as he has other things,” charged the former Secretary of State.

Kerry has repeatedly argued in favor of the Iran deal, which he helped broker while serving as Secretary of State.

Several months ago, he stated that the presentation of Iran's nuclear archive by Prime Minister Binyamin Netanyahu, in which Netanyahu proved that Iran's leaders had lied about their nuclear ambitions, showed why the deal must remain in place.

"Every detail PM Netanyahu presented yesterday was every reason the world came together to apply years of sanctions and negotiate the Iran nuclear agreement - because the threat was real and had to be stopped. It's working!" Kerry wrote.

Last November, Kerry warned Congress that it would be "extraordinarily dangerous" for it to reject the 2015 Iran nuclear deal.

He warned in late October that Trump risked driving Iran towards nuclear proliferation if he cancels the deal.