The Czech Republic has blocked an attempted purchase by Iran this year of a large shipment of sensitive technology useable for nuclear enrichment after false documentation raised suspicions.
UN experts and Western sources said the incident could add to concerns about whether Tehran can be trusted to adhere to a nuclear deal being negotiated with world powers under which it would curb sensitive nuclear work in exchange for sanctions relief.
Some details of the attempted purchase were described in the latest annual report of an expert panel for the United Nations Security Council's Iran sanctions committee, which has been seen by Reuters.
The panel said that in January, Iran attempted to buy compressors - which have nuclear and non-nuclear applications - made by US-owned company Howden CKD Compressors.
A Czech state official and a Western diplomat familiar with the case confirmed to Reuters that Iran had attempted to buy the shipment from Howden CKD in the Czech Republic, and that Prague had blocked the deal.
It was not clear if any intermediaries were involved in the attempt to acquire the machinery.
There was no suggestion that Howden CKD itself was involved in any wrongdoing. Officials at Prague-based Howden declined to comment on the attempted purchase.
The UN panel, which monitors compliance with sanctions, said there had been a "false end user" stated for the order. "The procurer and transport company involved in the deal had provided false documentation in order to hide the origins, movement and destination of the consignment with the intention of bypassing export controls and sanctions," it added.
A Czech official declined to say exactly how the transaction was stopped, provide specifications of the compressors or confirm the intended purchaser. However, he made clear it was the Czech authorities that halted the deal
The official, who spoke on condition of anonymity, said the total value of the contract would have been about 1.5bn Czech koruna (£39m, $61m).
The report offered no further details about the attempted transaction. Iran's UN mission did not respond to a query about the report.