"This is a former secretary of state engaged with the world's largest state sponsor of terrorism", Mr Pompeo said of Mr Kerry's meetings, adding that just last week Iran directed its militias in Iraq to fire Katyusha rockets at the USA consulate in Basra.
Kerry was an architect of the Iran nuclear deal that Trump withdrew from in May and has met several times with Iran's foreign minister since leaving office.
"Mr President, you should be more anxious about Paul Manafort meeting with Robert Mueller than me meeting with Iran's FM", Mr Kerry said on Twitter shortly after Mr Pompeo's remarks, referring to Mr Trump's former campaign chairman who yesterday agreed to co-operate with federal investigators into Russian meddling in the 2016 U.S. election.
In his tweet, Trump asked whether Kerry had complied with the Foreign Agents Registration Act. "Simply offering advice to a foreign government doesn't make you a foreign agent". In return, Iran agreed to restrictions on its nuclear program, along with rigorous inspections, arguably making it impossible for the Islamic regime to produce an atomic bomb.
Kerry also said that he thought Trump should have stayed in the Iran deal, arguing that under the deal "you have China, Russia, these other countries with you in the effort to leverage this different behavior from Iran rather than unilaterally pulling out and isolating yourself and making it much more hard to sit down with any Iranian".
When reports of Kerry's ex-officio contacts with Zarif first surfaced in May, Trump tweeted similar thoughts. Kerry replied with a chuckle, "I think everybody in the world is sitting around talking about waiting out President Trump", but he said that was in regard to other matters, not the Iran deal. "John Kerry can't get over the fact that he had his chance and blew it!"
Kerry is in the midst of a promotional tour for his new book, "Every Day is Extra", including stops in Los Angeles and Portland, Oregon, over the weekend.
"I'm confident that they met with their troika counterparts", Pompeo continued. "Stay away from negotiations John, you are hurting your country!" he said on May 8.
President Donald Trump has spoken out his dissatisfaction with the meetings.
Sure, Kerry now says he's merely "trying to elicit what Iran might be willing to do in order to change the dynamic in the Middle East for the better". You know, how does one resolve Yemen?