“My role...is to preserve the full implementation of the existing agreements. Again if something else can be built on it, this would be welcomed and accompanied by the European Union,” Mogherini told reporters during an EU foreign ministers meeting in Helsinki.
The deal has been in jeopardy since US President Donald Trump last year unilaterally pulled out of the accord and reimposed economic sanctions on Iran, seeking to push Tehran into wider security concessions including curbs on its ballistic missile program.
The move alarmed European powers, which says the deal has delivered, and infuriated the Islamic Republic.
The three European parties to the deal – Britain, France and Germany – along with the EU have repeatedly said they are committed to saving the deal, but efforts to shield Iran's economy from the reimposition of US sanctions have so far borne little fruit.
New hope of unblocking the political impasse emerged after Iran’s foreign minister made a flying visit for talks with host France at the G7 summit in Biarritz last Sunday.
At the summit, Trump indicated willingness to talk to Iran and Mogherini said the EU would support such a move – provided the current deal was preserved.
As well as mooting the summit with his Iranian counterpart Hassan Rouhani, Trump also appeared open to a French suggestion that Iran be given a line of credit to help stabilize its economy.
“If this new momentum is real, this can build on the work that we have been doing for years,” Mogherini said, referring to the existing treaty with Iran, called the Joint Comprehensive Plan of Action.
The 2015 nuclear deal between Iran and international powers on Iran’s nuclear activities in exchange for the lifting of many international sanctions on Tehran.
Mogherini declined to answer directly when asked if the United States now demanded that Iran do more than just going back in line with the existing deal’s commitments.
“Our work is to continue to ensure that there is full compliance from the Iranian side to its nuclear commitments,” she said.
Mogherini on Thursday gave a cautious welcome to the idea of US-Iran talks but stressed that "first and foremost what is existing needs to be preserved" – including the 2015 deal.
Ahead of the EU meeting, British Foreign Minister Dominic Raab said they would aim to "build on the momentum of the positive G7 talks on Iran."
"The nuclear deal is the only deal on the table that prevents Iran from getting a nuclear weapon and we will continue working together to encourage Iran to uphold the agreement in full," Raab said.
Iran says it has never sought nukes and that its nuclear program, as confirmed by the UN atomic agency, has no military dimensions and is solely for peaceful purposes including power generation.
All should play their part
Germany Foreign Minister Heiko Maas said on Thursday that his country welcomed signs the United States was more willing to discuss the Iranian nuclear deal and that every country, including Iran, should work to end the impasse.
“We welcome the result of the G7 summit in Biarritz, namely that the United States is more willing to talk... Everyone must contribute, including Iran, toward de-escalating the situation in the region and we want to play our part too,” Maas told reporters before the meeting of EU foreign ministers.
“Everything that contributes to a de-escalation is helpful. No side wants a war. We need to look into the situation in the Strait of Hormuz and we want to find as great as possible unity in the European Union,” Maas continued.
Reuters and AFP contributed to this story.