Trump administration outraged at John Kerry for talking to Iran

US Secretary of State Mike Pompeo on Friday lambasted his predecessor, John Kerry, for meeting Iranian officials in back-channel talks and accused him of trying to undermine the Trump administration's policy toward Tehran.

"What Secretary Kerry has done is unseemly and unprecedented," Pompeo told a news conference, adding that he "ought not to engage in that kind of behavior. It's inconsistent with what the foreign policy of the United States is, as directed by this president. It is beyond inappropriate."

Pompeo's crack at Kerry comes a day after President Donald Trump accused the former secretary of state of "illegal meetings with the very hostile Iranian Regime" in a late-night tweet.

"John Kerry had illegal meetings with the very hostile Iranian Regime which can only serve to undercut our great work to the detriment of the American people," Trump said on Twitter late on Thursday.

"He told them to wait out the Trump Administration!" he said, ending his Tweet with the word "BAD!"

Kerry, who negotiated the 2015 Iran nuclear deal which Trump scrapped this year, said during a tour to promote his new book "Every Day is Extra" that he had met Iranian Foreign Minister Mohammad Javad Zarif "three or four times" since he left office and Trump had entered the White House.

A spokesperson for Kerry said in a statement on Friday: "Kerry stays in touch with his former counterparts around the world just like every previous secretary of state.

"There's nothing unusual, let alone unseemly or inappropriate, about former diplomats meeting with foreign counterparts... What is unseemly and unprecedented is for the podium of the State Department to be hijacked for political theatrics," the spokesperson added.

Meanwhile, Kerry took to Twitter to respond to Trump, saying: "Mr. President, you should be more worried about Paul Manafort meeting with Robert Mueller than me meeting with Iran's FM. But if you want to learn something about the nuclear agreement that made the world safer, buy my new book."

Asked by conservative radio host Hugh Hewitt on Wednesday if he had offered Zarif advice on how to deal with Trump's decision to withdraw from the pact, Kerry replied: "No, that's not my job.”

"I've been very blunt to Foreign Minister Zarif, and told him look, you guys need to recognize that the world does not appreciate what's happening with missiles, what's happening with Hezbollah, what's happening with Yemen," he added, echoing the current administration's denunciation of Tehran's "malign" influence.

Conservative commentators immediately leapt on the act as evidence of "treason," with some calling for Kerry to go to prison.

Asked by a Republican lawmaker during a congressional hearing about the so-called shadow diplomacy, Manisha Singh, an assistant secretary of state, said Thursday: "It's unfortunate if people from a past administration would try to compromise the progress we're trying to make in this administration."

State Department spokeswoman Heather Nauert added: "I've seen him brag about the meetings that he has had with the Iranian government and Iranian government officials. I've also seen reports that he is apparently providing, according to reports, advice to the Iranian government. 

"The best advice that he should be giving the Iranian government is stop supporting terror groups around the world."