A Canadian-Iranian accountant who helped advise Iran’s negotiation team in talks that led to the 2015 nuclear agreement with the United States and other big powers has been sentenced to five years in prison for spying.

News of the conviction and sentence, reported today by Iran’s state-run Tasnim News Agency, did not identify the defendant by name, describing him only as a “spy who had infiltrated the team.”

But after news of the arrest first emerged in August 2016, Iranian lawmakers critical of the nuclear agreement identified the defendant as Abdolrasoul Dorri Esfahani, a dual citizen of Canada and Iran.

Esfahani was an adviser to Iran’s central bank and was believed to have helped the country’s nuclear negotiators bargain for the sanctions relief contained in the 2015 nuclear agreement.

Canadian news reports have described Esfahani as an accountant involved in financial aspects of the agreement, which ended or eased many sanctions in return for Iran’s reduced nuclear fuel enrichment and verifiable pledges of peaceful atomic energy use.

He was further described in some press accounts as a former diplomat at The Hague who had worked on resolving property disputes between the United States and Iran that predated the 1979 Islamic Revolution and the break in relations between the two countries.

The Tasnim report said that the defendant had been released on bail after his arrest and conviction by a lower court, but that an appeals court had upheld the ruling, so “the ex-negotiator will be put behind bars for five years on a charge of espionage.”

There was no immediate comment from the Canadian government to news of Esfahani’s upheld conviction and punishment. Philip Hannan, a spokesman for Global Affairs Canada, the department that oversees diplomatic matters, said in an email message that he was working with other departmental officials on a response.

Iran does not recognize dual citizenship for Iranians, which means that Esfahani’s Canadian passport does not afford him diplomatic protections, such as consular visits, that foreign prisoners receive in Iran. The same issue affects prisoners in Iran who are citizens of the United States and other countries.

Precisely what kind of financial information Iranian prosecutors say Esfahani betrayed — and to whom — is unclear.

Iran has been broadly unhappy that the eased sanctions specified in the nuclear agreement have not led to the huge economic boom the deal’s promoters in Iran had foreseen.

Iranian officials have complained that sanctions imposed by the United States that are not covered by the agreement, including long-standing restrictions on banking and financial transactions, have made many companies in other countries wary of investing in Iran.

President Donald Trump has denounced the agreement as an “embarrassment” that gave what he views as too many concessions to Iran, and he has hinted that he might withdraw the United States from the pact.

Other parties to the accord — Britain, China, France, Germany and Russia — as well as some of Trump’s own key advisers, have urged him to honor it.