Talks in Vienna resumed Thursday [April 15] with a JCPOA joint commission meeting lasting two hours and expert groups continuing work on plans to revive Iran’s 2015 nuclear deal with world powers. One group is identifying United States sanctions in violation of the agreement, which former President Trump abandoned in 2018, while another is deciding which steps taken by Iran in its nuclear program since 2019 go beyond the limits set by the deal, the JCPOA (Joint Comprehensive Plan of Action).

"Currently I think the nuclear working group is more advanced, much more advanced, than (the) sanctions-lifting working group," Wang Qun, China's ambassador to the United Nations International Atomic Energy Agency (IAEA), told reporters after a two-hour meeting of senior diplomats in the JCPOA’s the Joint Commission, representing the deal’s remaining signatories – China, Iran, Germany, France, Russia and the United Kingdom.

Talks in Vienna are complicated by the United States participating only indirectly, as both Tehran and Washington have said they will not engage in direct talks until the other side takes the first step in returning to the JCPOA. But the central challenge in the talks is deciding which sanctions introduced by Trump since 2018 contravene the deal.

Iran’s official IRNA news website quoted chief negotiator Abbas Araghchi as saying that the joint commission meeting was “challenging” and Iran expected Europeans to show more “goodwill”. He called for “practical” steps to quickly identify US sanctions that should be removed. He also repeated Supreme Leader Ali Khamenei's remarks on Wednesday that the talks should not "stretched" and become "attritional".

The most damaging of Trump’s measures – under what he called ‘maximum pressure’ – threatened secondary sanctions against anyone buying Iran’s oil or dealing with its financial sector. But the Trump administration levied a far wider web of measures, many linked to charges of ‘terrorism’, that officials openly said would complicate the task of any successor administration in trying to revive the JCPOA. Iran also argues that the US agreement under the JCPOA for it to receive the "full benefit" of sanctions-lifting was never honored by the US.

The Vienna talks resumed in the wake both of Sunday’s explosion at Iran’s Natanz nuclear facility, which was attributed to Israel by Iran and by Israeli media quoting intelligence officials, and Tehran’s announcement on Tuesday that it would increase its level of uranium enrichment to 60 percent.

While these moves have raised tensions – as is admitted by senior European diplomats – they may also concentrate minds. Calls from Iran’s hardline media to withdraw from the talks have been echoed by criticism in Israel of Prime Minister Benjamin Netanyahu, including from defense minister Benny Gantz, who demanded an enquiry into intelligence officials briefing the media. Enrique Mora, the European Union chief coordinator for the talks, said in a tweet it was good to see participants resume the talks "despite very challenging events and announcements over the past days."

The talks have no clear timeline. Iran’s Supreme Leader Ali Khamenei in a televised speech Wednesday evening said they should not be “stretched” or allowed to become “attritional.” Abbas Araghchi, the deputy foreign minister leading the Iranian delegation in Vienna, on Thursday evening reiterated opposition to the process becoming “attritional.”