Iran’s Foreign Minister Mohammad Javad Zarif got into a heated argument which evolved into a shouting match with his American counterpart, Secretary of State John Kerry, during nuclear talks this week, reports the Washington Free Beacon.

According to the report, the argument between the two was so intense that a Kerry aide “tip-toed into the room” to remind the men that everyone in the building could hear them shouting.

Zarif has lashed out at Western negotiators on many occasions, according to the Free Beacon. He reportedly “erupted” at EU negotiator Federica Mogherini when she mentioned Iran’s role in destabilizing the Middle East.

“Never try to threaten the Iranians,” Zarif yelled on another occasion when it was mentioned that the P5+1 could end the nuclear talks because of Iranian intransigence.

According to one Iranian negotiator, Zarif’s violent outbursts are “unprecedented” in the history of U.S. diplomacy. They have been known to cause alarm among Western bodyguards.

By continuing to shout at the other diplomats, Zarif is essentially ignoring an order from Iran’s Supreme Leader, Ayatollah Ali Khamenei.

Reports in February indicated that Khamenei had told Zarif to stop shouting and yelling at Kerry during negotiations on Iran’s nuclear program.

The Foreign Minister recounted back then to Iranian state media a conversation he had with the supreme leader.

“‘Why you are yelling in negotiations? Smile and speak,’” he recalled the supreme leader saying. “‘Do not quarrel on the negotiation table, reason with them,’” Khamenei continued, Zarif said.

The latest shouting match between the two top diplomats reportedly took place hours before Iran and world powers extended the deadline for a final agreement from Tuesday to Friday.

On Sunday, before the talks were extended again, Kerry had indicated that a nuclear agreement would be possible only if Iran makes the “hard choices” necessary and said Washington was prepared to walk away from talks if Iran fails to do so.