The United States on Wednesday imposed sanctions on Iranian Foreign Minister Mohammad Javad Zarif, with US Treasury Secretary Steven Mnuchin stating that Zarif “implements the reckless agenda of Iran’s Supreme Leader” and that the sanctions on him send “a clear message to the Iranian regime that its recent behavior is completely unacceptable”.

Iranian President Hassan Rouhani slammed the sanctions on Thursday, calling them “childish,” while claiming that Washington “is afraid of our foreign minister’s interviews.” Zarif himself Tweeted that hawkish elements in the Trump administration consider peace and dialogue with Iran an “existential threat.”

Tensions between Iran and the US and its allies have escalated in the past few months. Tehran recently started violating the 2015 Iran nuclear deal, which was abandoned by the Trump administration last year.

Read more: Iran says U.S. sanctioning of top diplomat ‘childish’ as tensions rise