Iran’s stock of low-enriched uranium – used for peaceful purposes, but when further processed for a weapon – did not exceed the agreed limit of 300kg, the report said.

It added that Iran “has not pursued the construction of the Arak ... reactor” – which could give it weapons-grade plutonium – and has not enriched uranium above low purity levels.

The landmark deal was signed in July 2015 by Iran and five permanent members of the United Nations Security Council – Britain, China, France, Russia and the US – plus Germany, establishing controls to prevent Tehran from developing an atomic bomb.

The EU’s diplomatic chief Federica Mogherini said Iran’s compliance with the accord had been verified on at least eight separate occasions.

It is time to “invest in international cooperation” and “open new channels and not destroy the ones we already have”, she said by video conference.

It is “certainly not the time to dismantle them”.

Faced with the growing threat from North Korea, “we cannot afford to open a new front”, Mogherini said.

Trump is a fierce critic of the 2015 accord, which he has called “the worst deal ever”, and he is expected to announce that he is “decertifying” Iran’s compliance with it.

US officials insist this will not sink the deal itself but open the way for Congress to possibly develop new measures to punish other aspects of Iran’s behaviour.

Congress requires the president to certify Iranian compliance with the deal every 90 days. The next certification date is October 15.

Under the law, Congress would then have 60 days to decide whether to reimpose sanctions lifted by the deal.