Since the United States unilaterally withdrew from the agreement, officially known as the Joint Comprehensive Plan of Action (JCPOA), it could not be considered a part of it, a spokeswoman for EU foreign policy chief Josep Borrell said on Sunday.
"Given that the US unilaterally withdrew from the JCPOA in May 2018 and has not participated in any JCPOA structures or activities subsequently, the US cannot be considered as a JCPOA participant.
"We therefore consider that the US is not in a position to resort to mechanisms reserved for JCPOA participants (such as the so called snapback)."
Also Iran has accused US President Donald Trump of endangering the current world order with what it terms his planned sabotage of the Vienna nuclear agreement with the aid of the so-called "snapback" mechanism. Tehran maintains that Trump's strategic goal is not only to torpedo the 2015 nuclear agreement between major world powers and Iran, but also to enforce unilateralism and thus change the world order.
"All countries should show solidarity in order to defend the reputation of the UN," Diako Hosseini, political advisor in the Tehran presidential office, tweeted on Sunday.
The nuclear agreement is intended to prevent Iran from developing nuclear weapons, but it grants the Islamic Republic an internationally monitored civilian nuclear power programme.
In the course of the agreement adopted by the United Nations, the dismantling of sanctions against Iran was also regulated. An arms embargo that is part of the deal is due to expire in October. The US wants an extension of the embargo, but it failed to push this through in the UN Security Council.
Now Trump wants to force the reinstatement of all international sanctions on Iran against the will of the other members of the UN Security Council via a mechanism known as a snapback.
"We'll be doing a snapback," Trump told reporters on Saturday at a press conference in New Jersey. "You'll be watching it next week."
The snapback was granted to the participants in the nuclear agreement in the event that Iran violates it. However, under Trump, the United States withdrew unilaterally from the agreement in 2018.