Iran has told Europe it will not reverse its decision to increase uranium enrichment beyond the limits set by the 2015 nuclear accord until it achieves its “full rights” to an economic relationship with the EU under the deal.

Ali Shamkhani, a senior security official and representative of Iran’s supreme leader, made his remarks as he met a senior French diplomat sent to Tehran by the French president, Emmanuel Macron.

Iran’s president, Hassan Rouhani, also warned the UK it would face as yet unspecified consequences as a result of the UK’s seizure of an oil tanker bound for Syria off the coast of Gibraltar last week. The ship remains in British possession.

Shamkhani’s warning suggests the three European powers – France, Germany and the UK – face an uphill struggle to keep the nuclear deal alive. Shamkhani said the Iranian strategy could not change, and claimed European countries had shown a lack of will to keep their side of the bargain.

Meanwhile, Donald Trump threatened to crank up sanctions substantially and accused Iran of “secretly” enriching uranium in breach of the nuclear accord.

“Iran has long been secretly ‘enriching’, in total violation of the terrible 150 Billion Dollar deal made by John Kerry and the Obama Administration,” Trump said on Twitter. “Sanctions will soon be increased, substantially!”

The 2014 deal imposed the most intrusive nuclear supervision in any country, and there has been no serious suggestion from elsewhere that Iran is secretly enriching uranium.

Kazem Gharib Abadi, Iran’s ambassador to the International Atomic Energy Agency, said that all Tehran’s nuclear activities were being monitored by inspectors from the agency. “We have nothing to hide,” he said after an IAEA meeting in Vienna, which was called at the request of Washington.

The two-day visit to Tehran by the French envoy, Emmanuel Bonne, was seen as probably the last attempt to broker a deal before Europe decided to put Iran’s actions into the formal dispute mechanism of the Joint Comprehensive Plan of Action (JCPOA).

If the dispute mechanism is unable to resolve the differences, it is likely the EU will restore sanctions against Iran that were taken off when the deal was first signed.

Q&A What is Iran's nuclear enrichment cap? Show Under the joint comprehensive plan of action signed in 2015, Iran is only permitted to produce low-enriched uranium. This is uranium that has a concentration of 3%-4% of the isotope U-235. This isotype is a fissile material, which is capable of sustaining a nuclear fission chain reaction. At this low level of enrichment, it can be used to produce fuel for nuclear power plants. Iran is permitted to stockpile 300kg of it, at an enrichment level capped at 3.67%. A bomb needs uranium that is up to 90% enriched. Iran’s atomic energy agency has said production of enriched uranium has been quadrupled. The more that uranium is enriched, the faster it is to enrich it further. Iran argues that it is no longer bound by the cap because of the withdrawal of the US from the agreement, and the reimposition of economic sanctions Donald Trump.

Read more: Iran's uranium enrichment programme: the science explained

Tehran has been demanding that the EU do more to compensate Iran for Donald Trump’s decision to pull out of the deal last year, a withdrawal followed by a US attempt to impose maximum economic pressure on Tehran, including a worldwide ban on the purchase of Iranian oil exports.

Shamkhani, secretary of the Supreme National Security Council (SNSC), told Bonne on Wednesday that Tehran regarded Iran’s action as within the terms of the JCPOA because the country was entitled to downgrade its commitments if the other side failed to meet their own.

Iran has been frustrated by the slow European progress in setting up a long-planned financial mechanism designed to circumvent the impact of US secondary sanctions on firms that seek to trade with Iran.

Q&A What is Iran's nuclear enrichment cap? Show Under the joint comprehensive plan of action signed in 2015, Iran is only permitted to produce low-enriched uranium. This is uranium that has a concentration of 3%-4% of the isotope U-235. This isotype is a fissile material, which is capable of sustaining a nuclear fission chain reaction. At this low level of enrichment, it can be used to produce fuel for nuclear power plants. Iran is permitted to stockpile 300kg of it, at an enrichment level capped at 3.67%. A bomb needs uranium that is up to 90% enriched. Iran’s atomic energy agency has said production of enriched uranium has been quadrupled. The more that uranium is enriched, the faster it is to enrich it further. Iran argues that it is no longer bound by the cap because of the withdrawal of the US from the agreement, and the reimposition of economic sanctions Donald Trump.

Read more: Iran's uranium enrichment programme: the science explained

The EU says the slow progress is due to technical and legal difficulties, and not an absence of political will, but Tehran has been losing faith.



Shamkhani insisted Iran would resist US pressure, saying: “Iran has in practice proved that in economic, political and defence dimensions it has the ability and capacity to manage and deal with various tensions and challenges. You cannot speak the language of force.”

The oil tanker seized by Gibraltar and UK authorities was thought to be heading to Syria. Photograph: A Carrasco Ragel/EPA

Last week, UK authorities in Gibraltar intercepted an Iranian supertanker that was believed to be breaching EU sanctions by carrying a shipment of Tehran’s crude oil to war-ravaged Syria. Royal Marines helped seize the tanker, together with Gibraltar police.

Rouhani was quoted by the Iranian official IRNA news agency on Wednesday calling the seizure of the Iranian oil ship “mean and wrong”. During a cabinet meeting he warned London: “You are an initiator of insecurity and you will understand its repercussions.”