Britain, France and Germany warned Iran against any further breaches of the international nuclear deal signed in 2015, according to reports on Friday.
During a meeting at UN General Assembly in New York, the three EU signatories to the deal said that they would trigger a special dispute mechanism if there were further violations, the BBC reported.
Iran has already taken three separate calibrated steps away from the deal and has warned it will take a fourth in November unless the US lifts economic sanctions.
Iran said that it has been taking advertised, reversible and calibrated steps away from the deal as a reprisal for US sanctions, including its ban on Iranian oil exports, and the failure of the EU to do more to build trade with Iran.
The EU warning also came after the French president, Emmanuel Macron, failed to broker a new deal between the US and Iran in which Washington would lift sanctions, and the Tehran would return to full compliance with the agreement.
Macron had hoped the shock of the attack on the Saudi oil fields, ascribed to Iran by both the EU and the US, would jolt the two sides into compromise.
The UN nuclear watchdog said that Iran was using banned enrichment technology.
If the dispute mechanism is triggered, the entire nuclear agreement could collapse and the UN could reinstate sanctions on Iran, which would be applied by all UN member states.