Iran said on Thursday three European states had succumbed to “high school bully” Donald Trump when they triggered a dispute mechanism in a nuclear pact the U.S. president opposes, a step that could eventually lead to reimposing U.N. sanctions.

The pact, known as the JCPoA, was agreed in 2015 between Tehran and world powers, offering Iran relief from sanctions if it curbed its nuclear work. Trump withdrew from the deal in 2018 and reimposed U.S. sanctions, telling Tehran he wanted a more stringent deal on nuclear and other issues.

Iran has responded to the U.S. sanctions by scaling back its compliance with the deal, culminating with an announcement this month that it would reject all limits on production of enriched uranium, although it says it wants to keep the deal in place.

Britain, France and Germany triggered the deal’s dispute mechanism this week. London said it was now time for a “Trump deal” to replace it, while Paris said broad talks were needed.

The Washington Post reported on Wednesday that Trump’s administration had threatened to impose a 25% tariff on European automobile imports if Britain, France and Germany did not formally accuse Iran of breaking the nuclear deal.

“Appeasement confirmed. E3 sold out remnants of #JCPOA to avoid new Trump tariffs. It won’t work my friends. You only whet his appetite. Remember your high school bully?” Iranian Foreign Minister Mohammad Javad Zarif wrote on Twitter.

Two European diplomats confirmed Washington had threatened tariffs but said leaders of the three European states had already decided to trigger the mechanism before that.

A third diplomat said such U.S. tactics only undermined the Europeans, who are trying to apply pressure independently.

“True or not it has the effect of discrediting the Europeans, but then Trump doesn’t really care about that,” the diplomat said. “From the Iranian side, it just proves that only the U.S. matters in this.”