Tehran (AFP)

An audiotape of Iran's top diplomat bemoaning the military's influence was leaked to sow "discord" during talks on reviving an international nuclear deal, President Hassan Rouhani said Wednesday, after the recording stirred domestic controversy.

The recording of Foreign Minister Mohammad Javad Zarif was published by media outside Iran ahead of presidential elections.

The talks in Vienna are aimed at getting the United States to return to the agreement it abandoned under former president Donald Trump, and Iran to resume full compliance with nuclear obligations it retreated from in response.

Rouhani said the audio was leaked just as the Vienna talks were "at the height of their success, so that it creates discord inside" the Islamic republic.

"We can only lift sanctions through unity," the president said.

Zarif has been under fire since the audiotape emerged on Sunday, with comments he made about Qasem Soleimani, the commander of the Revolutionary Guards' foreign operations arm who was killed in a US air strike last year, hitting a nerve.

"In the Islamic republic the military field rules," Zarif said in the recording, quoted by the New York Times. "I have sacrificed diplomacy for the military field rather than the field servicing diplomacy."

Zarif, seen as the architect of the 2015 nuclear accord, has been mentioned as a possible contender in the June 18 presidential election, although he has said he does not plan to run.

- 'Domestic infighting' -

Known formally as the Joint Comprehensive Plan of Action, or JCPOA, the landmark 2015 deal between Iran and six world powers promised Iran relief from sanctions in exchange for curbs on its nuclear programme.

But the accord started to unravel in 2018 when Trump pulled out of it and imposed wave afer wave of sanctions on Iran, which retaliated a year later by ramping up its nuclear activities.

In his first public reaction to the audiotape, Zarif took to social media to downplay the recording while voicing regret that it had triggered "domestic infighting".

But despite a furious reaction from conservatives, he stuck to much of what he said in the recording, saying he favours a "smart adjustment" between the military and diplomatic spheres.

In a post on Instagram, Zarif said an "honest and passionate" argument in a private setting had been misconstrued as "personal criticism".

The veteran diplomat said the "main point" of his remarks was to emphasise "the need for a smart adjustment of the relationship between" diplomacy and the military.

Zarif, who has been on a tour of neighbouring states this week, also said he saw a need for "setting priorities through legal structures and under the great purview of the supreme leader" Ayatollah Ali Khamenei.

- 'Not government views' -

Rouhani, who has ordered a probe into who leaked the "stolen" recording, praised Zarif for his track record and achievements, but also set out his position on the relationship between Iran's military and diplomacy.

He said the "difficult path" of nuclear talks "was trodden with the sacrifice, selflessness and resistance of diplomats and today at the helm of this movement, is a knowledgable person familiar with issues like Dr. Zarif."

But "the (military) field and diplomacy are not two fields against each other," Rouhani stressed.

Some of the views in the recording "are not the views of the government or the president. Any minister or official might have some views" of their own, the president said.

"If someone thinks that it is (a choice between) the (military) field or diplomacy, foreign policy or defensive policy, or that the (military) field must succeed or the negotiations -- this is not an accurate thing to say," he said.

"Two hands ultimately come together and do one thing," he said, emphasising that there was a "system and a framework" of discussing issues in both fields in Iran's Supreme National Security Council.

"In a free country like Iran we freely express our opinions in our meetings," Rouhani said.