Donald Trump threat to decertify the nuclear agreement stance put him at odds with key US allies, including Britain, France, Germany, Russia and China.
Iran, US allies in Europe and Russia have defended the 2015 nuclear agreement with Tehran and said they would stick by it, after US President Donald Trump threatened to terminate the agreement.
Trump said in a Washington speech that he would not certify that Iran is complying with its agreement with six world powers and the European Union, despite a determination by the UN's nuclear watchdog that Tehran is meeting the deal's terms.
The Republican president threw the issue to the US Congress, which has 60 days to decide whether to reinstate US sanctions. He warned that if "we are not able to reach a solution working with Congress and our allies, then the agreement will be terminated".
Iranian President Hassan Rouhani said Iran will remain committed to the multinational deal as long as it serves the country's national interests.
Trump's decision to decertify the deal will isolate the United States, as other signatories of the accord remained committed to it, Rouhani said in a live television address. The deal was not renegotiable, he said.
The agreement, negotiated by Trump's Democratic predecessor Barack Obama, eased sanctions on Tehran in returns for strict limits on its nuclear program.
Trump's stance put him at odds with key US allies, including Britain, France and Germany who, along with Russia and China, negotiated the deal with Iran alongside the European Union.
In Brussels, EU foreign policy chief Federica Mogherini said Washington could not unilaterally cancel the agreement.
"We cannot afford as the international community to dismantle a nuclear agreement that is working," said Mogherini, who chaired the final stages of the landmark talks. "This deal is not a bilateral agreement.
"The international community, and the European Union with it, has clearly indicated that the deal is, and will continue to be, in place," Mogherini told reporters in Brussels.
The leaders of Britain, France and Germany issued a joint statement warning the United States against taking decisions that could harm the nuclear deal such as re-imposing sanctions.
The three leaders also said they shared US concerns over Iran's ballistic missile program and regional destabilising activities and were ready to work with Washington to address those concerns.
French President Emmanuel Macron's office said he had spoken with Rouhani by telephone and assured him of France's commitment to the deal, but that Tehran must strictly comply with it.
Russia's foreign ministry said there was no place in international diplomacy for threatening and aggressive rhetoric, and said such methods were doomed to fail, in a statement issued after Trump's speech.
The ministry said Trump's decision to de-certify the deal would not have a direct impact on implementation of the agreement but that it ran counter to its spirit.
The head of the UN's International Atomic Energy Agency said Iran was complying with the accord, formally known as the Joint Comprehensive Plan of Action, under the world's "most robust nuclear verification regime".
"The nuclear-related commitments undertaken by Iran under the JCPOA are being implemented," Yukiya Amano, director general of the IAEA said in a statement.
Trump received support from Israel, Saudi Arabia, the United Arab Emirates and Bahrain, all of which oppose what they say are Iran's expansionary moves in the Middle East.
"President Trump has just created an opportunity to fix this bad deal, to roll back Iran's aggression and to confront its criminal support of terrorism," Israeli Prime Minister Benjamin Netanyahu said in a video statement.