The incident could add to Western 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.

The negotiators are trying to reach a deal by the end of June after hammering out a preliminary agreement on April 2, with Iran committing to reduce the number of centrifuges it operates and agreeing to other long-term nuclear limitations.

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 the U.S.-owned company Howden CKD Compressors.