DUBAI/PARIS - 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 US president opposes, a step that could eventually lead to reimposing UN 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 US sanctions, telling Tehran he wanted a more stringent deal on nuclear and other issues. Iran has responded to the US 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 US 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 US matters in this."'SNAPPING BACK'The Europeans have long opposed Trump's decision to withdraw from the nuclear deal, but have been threatening for months to trigger the dispute mechanism if Iran did not comply with it.The dispute mechanism begins a complex diplomatic process that can end with UN sanctions on Iran "snapping back" into place, although the Europeans say that is not their aim.In triggering the dispute mechanism, the European countries said they were not backing a US policy of "maximum pressure" on Iran, and they still hope to salvage the nuclear deal.The nuclear dispute lies at the heart of Iran's long-running standoff with the West that spiralled into open conflict this month when Washington killed an Iranian general in Baghdad and Tehran responded with missile strikes on US targets in Iraq.During that period of high alert, Iran shot down a civilian airliner in what it now says was a tragic mistake. This has triggered anti-government protests at home.Enriched uranium can be used to create material for nuclear warheads. Iran denies Western accusations it wants such weapons and says it wants nuclear material for peaceful purposes."We are enriching more uranium than before the deal was reached," President Hassan Rouhani said in a televised speech. "Pressure has increased on Iran but we continue to progress."US sanctions meanwhile have hammered Iran's economy. Washington aims to reduce its oil exports to zero.British Prime Minister Boris Johnson said that, if the 2015 pact were scrapped, "let's replace it with the Trump deal".France said the only way to resolve the crisis between the United States and Iran was for Tehran to accept a broad negotiation and Washington to progressively reduce sanctions.Iran has repeatedly said it will not talk with sanctions in place, and cannot negotiate with Trump who broke US promises by abandoning the previous deal.