It prompted criticism from the Iranian president, who said the focus should be firmly on US policies.
The International Atomic Energy Agency's 35-nation board of governors held talks in Vienna at the request of the US, which abandoned the 2015 pact last year and began imposing strict sanctions on Tehran, diplomatic sources told Efe news.
The convening members are not expected to adopt any resolutions on this occasion, although they could agree on a joint statement calling on Tehran to backtrack on its decision to breach the deal and expand its nuclear programme, which it decided to do as a response to US sanctions.
Germany, France, Britain and the European Union on Tuesday called on Iran to return to the full commitment of the 2015 Joint Comprehensive Plan of Action (JCPOA).
But Iran's President, Hassan Rouhani, took issue with the meeting's agenda.
"It isn't necessary for you to be worried about Iran, your concern should be with the US, which has shot down the JCPOA and has undermined all of its commitments," he told members of the cabinet in a weekly meeting.
He described the meeting as laughable, given it was the US that pulled out of the accord and levelled sanctions against Iran.
His Foreign Minister, Mohammad Javad Zarif, said it was impossible to negotiate "under pressure" and called on the US to end its campaign of "economic terrorism against Iran."
US President Donald Trump's administration pulled out of the 2015 nuclear deal - which bore the signature of his predecessor Barack Obama - in May 2018.
He then reactivated sanctions against Tehran and drew up new ones squeezing its oil and banking sectors.
Rouhani marked the anniversary of Trump's decision by announcing that Iran would start to ignore some of the stipulations in the deal if the remaining signatories failed to keep their commitments and offset US sanctions within the next 60 days.
On Monday, the Vienna-based IAEA confirmed that Iran had exceeded the limits on its stockpile of low-enriched uranium, which can be used as fuel in nuclear reactors or to make atomic bombs.
According to the deal, Tehran had to sell off any amount of uranium that surpassed the 300 kg restriction.
Originally signed by Iran and the five permanent members of the UN Security Council, China, France, Russia, the UK, and the US, plus Germany, the deal saw Tehran swap in much of its nuclear programme for the slight alleviation of international sanctions against it.
It prompted immediate ire from Iran's regional foes like Israel.
Trump's decision to withdraw from the accord preceded a downward spiral in US-Iran relations.
In the intervening year, US officials have accused Iran and Iranian proxies of committing several acts of sabotage against Washington's allies in the region and, in June, Iranian forces shot down an unmanned US surveillance drone.
Iran said the aircraft had entered its airspace whereas the US said it had been flying in international territory over the Strait of Hormuz, one of the busiest lanes in global oil trade and a flashpoint for US-Iran tensions.
( With inputs from IANS )