Iran has said it is determined to proceed with its ballistic missile programme, as it rejected as a "desperate falsehood" the letter from three European countries accusing Tehran of developing missiles capable of delivering nuclear warheads.
The ambassadors for the United Kingdom, Germany and France to the UN Security Council called on UN chief Antonio Guterres to inform the council in his next report that Iran's missile programme was "inconsistent" with a UN resolution underpinning a currently unravelling nuclear deal reached in 2015 between Iran and six world powers.
Iranian officials on Thursday responded defiantly after the letter circulated the previous day, asserting that Tehran was determined to proceed with its ballistic missile programme, which it has repeatedly described as defensive in purpose and unrelated to its nuclear activity.
"Iran is determined to resolutely continue its activities related to ballistic missiles and space launch vehicles," Iranian UN envoy Majid Takhte Ravanchi said in a letter to Guterres.
Meanwhile, Iranian Foreign Minister Mohammad Javad Zarif denounced the European powers' intervention.
"Latest E3 letter to UNSG on missiles is a desperate falsehood to cover up their miserable incompetence in fulfilling bare minimum of their own #JCPOA obligations," Zarif tweeted, using the abbreviation "E3" for the three European parties to the nuclear agreement, and referring to the deal by its formal acronym, the Joint Comprehensive Plan of Action.
He urged the UK, France and Germany not to bow to "US bullying".
The resolution cited by the European countries passed the same year Iran signed the nuclear deal with the United States, UK, Germany, France, Japan, China and Russia, in which Tehran agreed to curtail its disputed uranium enrichment programme in return for relief from sanctions.
The letter surfaced at a time of heightened friction between Iran and the West, with Tehran rolling back its commitments under the deal step by step in response to US President Donald Trump's pullout from the pact last year and the imposition of a "maximum pressure" sanctions campaign against the Islamic Republic that has crippled its economy.
"The 2015 nuclear deal does not address Iran's ballistic missile programme," Al Jazeera's Asead Baig, reporting from Tehran, said.
"Iran was very clear that they only wanted to concentrate on Iran's nuclear programme, and it's one of the reasons why Trump has criticised the deal and one of the reasons he cited for pulling the US out of it. What does address Iran's ballistic programme is the United Nations resolution that endorsed that 2015 deal and that's what the Europeans say Iran is in violation of."
Upcoming UNSC meeting
The Security Council is due to meet on December 20 to weigh the state of Iran's compliance with the resolution in question, and the European letter "will add to that discussion", a senior European diplomat told Reuters News Agency.
The ambassadors' letter specifically cited testing on a Shahab-3 medium-range ballistic missile variant "equipped with a manoeuvrable re-entry vehicle". Footage of a previously unseen flight test was released on social media on April 22, the letter said.
"The Shahab-3 booster used in the test is a Missile Technology Control Regime category-1 system and as such is technically capable of delivering a nuclear weapon," the letter added.
A 2015 report by the IAEA on the possible military dimensions of Iran's nuclear programme concluded "that extensive evidence indicated detailed Iranian research in 2002-2003 on arming the Shahab-3 with a nuclear warhead", the letter said. It went on to cite three other missile test in July and August that strained compliance with the resolution.
Some countries on the UNSC, including Russia, which with four other world powers wields a veto, argue that the language does not make the stipulations of the resolution obligatory.
Meanwhile, Russian state nuclear company Rosatom's nuclear fuel cycle unit TVE said in a statement on Thursday it had suspended work on revamping a factory at Iran's Fordow nuclear complex due to an issue with uranium compatibility.
"Uranium enrichment and the production of stable isotopes cannot be carried out in the same room," TVEL said, adding that it was "technologically impossible" to implement the project at this time.
In November, the US said it would cease waiving punitive sanctions related to the Fordow plant from December 15 - a move Russia condemned - after Tehran resumed uranium enrichment at the underground site as it took another step away from the nuclear deal in the wake of Washington's withdrawal.