On Tuesday, Iranian Foreign Minister Mohammed Javad Zarif fired back at President Donald Trump and dismissed his angry warning that Tehran risked consequences “the like of which few throughout history have suffered before” if it made threats against the United States.

Zarif responded via Trump’s favorite medium Twitter, saying “COLOR US UNIMPRESSED,” employing Trump’s penchant to use all capital letters in his tweets. Zarif also echoed the exact words from Trump, saying, “BE CAUTIOUS.”

According to CNN, when asked if Trump risked inciting war with Iran, White House press secretary Sarah Huckabee Sanders told reporters Monday morning, “if anybody is inciting anything, look no further than to Iran.”

“The President’s been, I think, pretty strong since day one in his language toward Iran. He was responding to comments made from them, and he’s going to continue to focus on the safety and security of American people,” Sanders said at the White House briefing. She declined repeated questions about whether Trump would consider meeting with Rouhani, CNN reported.

Tensions between the U.S. and Iran date back before the Trump administration. However, the relationship has grown heated following Trump’s withdrawal of the U.S. from the Iran nuclear deal earlier this year. The Obama-era agreement eliminated sanctions on Iran in exchange for the nation abandoning its nuclear program. Every other country in the pact has said it will uphold the deal.