The planned July 28 meeting is aimed at salvaging the hard-won deal, on life-support since the US withdrew from it last year and reimposed biting sanctions against Iran.
Amid rising hostilities with the United States, Iran's Revolutionary Guards on Friday seized a tanker sailing under the flag of US ally Britain.
State television aired new footage of the crew aboard the Stena Impero which Iran has impounded at its port of Bandar Abbas for allegedly breaking "international maritime rules".
In the video, the crew of 18 Indians, three Russians, a Latvian and a Filipino are seen sitting around a table and seemingly going about their daily routines.
The seizure of the Swedish-owned vessel has been seen as a tit-for-tat move after British authorities detained an Iranian tanker on July 4 in the Mediterranean on suspicion it was shipping oil to Syria in breach of EU sanctions.
"Throughout history, Iran has been and will be the main guardian of security and free navigation" in the Gulf, President Hassan Rouhani said late Monday.
"There is still no adequate and lasting stability and security in the region," he added, emphasising Tehran was not seeking to stoke tensions.
The head of Iran's navy said in an interview published Tuesday that Iran closely observes "all enemy ships" going through the Gulf using drones.
"We observe all enemy ships, especially America's, point-by-point from their origin until the moment they enter the region," Rear Admiral Hossein Khanzadi said, quoted by YJC news agency.
"We have complete images and a large archive of the daily and moment-by-moment movements of coalition forces and America."
Iran's civil defence chief Gholam Reza Jalali said the seizure of the UK-flagged tanker marked the "end to British rule in seas."
- Trump dismisses spy claims -
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Since the US began reimposing sanctions on Iran, tensions have mounted with drones shot down and tankers mysteriously attacked in the sensitive waters of the oil-rich Gulf.
US President Donald Trump called off air strikes against Iran at the last minute in June after the Islamic republic downed a US drone.
Iran also said Monday it had arrested 17 suspects and sentenced some to death after dismantling a CIA spy network -- claims Trump dismissed as "totally false".
The nuclear deal meeting was requested by the European parties to discuss the "new situation", Iran said, referring to its reduced nuclear commitments under the deal in response to the US withdrawal.
"It was agreed to convene an extraordinary meeting of the JCPOA joint commission in Vienna on July 28," Iran's foreign ministry said, using the acronym for the deal's formal name, the Joint Comprehensive Plan of Action.
The EU confirmed Iran would meet envoys from Britain, China, France, Germany and Russia -- the remaining parties to the deal -- in Vienna on Sunday.
Tehran has already given up on complying with some of the deal's limits on its nuclear programme in retaliation for the US withdrawal and what it sees as the failure of remaining parties to help it circumvent sanctions.
- 'De-escalation' -
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Iran's deputy foreign minister Abbas Araghchi has left for France to deliver a message from Rouhani to his counterpart Emmanuel Macron, the ministry's spokesman tweeted Tuesday, without elaborating.
Macron's top diplomatic adviser Emmanuel Bonne visited Iran on July 9 to "piece together a de-escalation" strategy and met top Iranian officials.
The 2015 deal curbed Iran's nuclear programme in exchange for sanctions relief.
But on May 8 -- more than a year after the US withdrawal -- Iran said it would disregard certain limits on the programme as it was not receiving any benefits.
Iran has threatened further measures if the remaining parties to the deal fail to help it circumvent US sanctions, especially to sell its oil.
It has since exceeded the deal's limits on its enriched uranium and heavy water stockpiles, as well as passing a cap on its uranium enrichment.
The 4.5 percent enrichment level it reached is well below the more than 90 percent required for a nuclear warhead.
Iran has yet to specify what other steps it may take, and has repeatedly emphasised its actions can be reversed "within hours" if European partners deliver on commitments.
Meanwhile, China described as "illegal" US sanctions imposed on its companies as part of Washington's campaign against Iran.