Iran is obstructing a UN investigation into a secret nuclear warehouse that was revealed by Israeli Prime Minister Benjamin Netanyahu last year and refusing to answer a nuclear watchdog's questions, according to a new report.
The UN is investigating whether the Iranian government set up a site in Tehran to store equipment and material for nuclear work, in contravention of the 2015 nuclear deal that put limits on its uranium enrichment programme.
But Iran is failing to provide answers to inspectors from the International Atomic Energy Agency, the body that oversees the deal's implementation, The Wall Street Journal reported late on Monday.
The obstruction is the first time that Iran failed to comply with nuclear inspectors since the deal came into force in January 2016.
The revelation comes at a crucial moment for the milestone 2015 deal between Tehran and world powers. Iran has moved away from its responsibilities under the agreement and has given its remaining European signatories a Friday deadline to offer it new terms before it takes a "strong step" away from the deal.
Iran denied Mr Netanyahu's claims about a secret nuclear warehouse in Tehran, which he presented on a large screen to much media attention.
The US withdrew from the nuclear deal in May last year after Mr Netanyahu's allegations and imposed two rounds of sanctions on the Iranian economy. The restrictions stoked Iranian anger and Tehran responded with attacks on tankers in the Gulf, watering down its commitments to the nuclear deal and shooting down a US drone.
In recent weeks, the possibility of a US-Iran meeting to ease tensions has been raised but Tehran is demanding that sanctions be lifted before any such summit can take place.
Iran's President Hassan Rouhani on Tuesday ruled out holding bilateral talks with the US, saying his country is opposed to such negotiations in principle.
In an address to parliament, Mr Rouhani also said Iran was ready to further reduce its commitments to the 2015 deal "in the coming days" if current negotiations yield no results by Thursday.
European parties to the deal have struggled to calm the deepening confrontation between Iran and the US and save the deal by shielding Tehran's economy from the sanctions.
But Iran said on Monday that its views have been converging with those of France on ways to save the agreement.
French President Emmanuel Macron has been trying to convince the US to offer Iran some sort of relief from its sanctions.
"In the past few weeks, there have been serious negotiations", between Mr Rouhani and Mr Macron, as well as talks with other European nations, government spokesman Ali Rabiei said.
"Fortunately, in many areas, our views have come closer together," he said.