The US has violated the body and spirit of the nuclear deal signed in July 2015 between Tehran and six major international powers, a senior Iranian cleric said on Friday.
Ayatollah Ahmad Khatami was responding to US President Donald Trump's Thursday statement accusing Tehran of "not upholding the spirit of the nuclear deal".
Trump said he was about to decide on certifying the Iran nuclear deal or Joint Comprehensive Plan of Action (JCPOA) and said that there was a need to put an end to Tehran's aggression and nuclear ambitions, Efe news reported.
The ayatollah, who is an important member of the Assembly of Experts, said that Iranian leaders agreed that the JCPOA could not be renegotiated. Khatami also warned that Europe's support could not be taken for granted and it would choose the US over Iran if forced to.
Only the US government has opposed the nuclear deal, which has the support of five other signatories: Russia, China, France, the United Kingdom and Germany.
Ali Akbar Salehi, vice-president of the Atomic Energy Organization of Iran, appealed to all parties on Thursday to continue with the deal if they wish to persuade North Korea to come to the negotiating table.
Salehi said that if other countries also withdraw from the deal, the JCPOA will collapse, but if it is only Washington that leaves, the joint supervising commission can decide further course of action.
Trump has until October 15 to decide on certifying whether Iran is fulfilling the terms of the agreement, which puts restrictions on its nuclear capabilities in exchange for lifting international sanctions.
A US decision to not certify Iran will not mean its withdrawal from the pact, but will start a process which can culminate in a re-imposition of sanctions on Iran for its nuclear programme, a step which would probably put an end to the deal.
Many media outlets reported that the Trump administration is planning to de-certify Iran, citing US national interests.
"We hope that the final decision that the US President adopts will be weighed and based on reality, because it is an extremely necessary programme," Russia's Foreign Minister Sergey Lavrov said on Friday.