Israel has sent officials to Vienna to meet participants in talks trying to revive the 2015 Iran nuclear deal, which Israel has opposed.

Nour News – an official Iranian outlet affiliated to the Supreme National Security Council –tweeted that “the overt and unexpected presence of the Zionists in Vienna is undoubtedly a deterrent to progress in the current sensitive situation.”

The Israeli delegation, headed by Joshua Zarka, the foreign ministry’s deputy director general for strategic affairs, met Tuesday with Mikhail Ulyanov, Russia’s top negotiator in the Vienna talks, and Monday with Rafael Grossi, director-general of the International Atomic Energy Agency (IAEA). Although Israel is a member of the IAEA, its nuclear arsenal is not subject to IAEA monitoring as Israel is not a signatory of the Nuclear Non-Proliferation treaty.

Ulyanov played down the significance of Zarka’s trip, tweeting that he had met with “Israeli colleagues from the capital and their Permanent Mission in Vienna” to discuss issues related to the IAEA. Russia has long called on both Iran and the US to return to the JCPOA.

Zarka tweeted in reply: “Thank you for a frank and important discussion.”

The Israeli delegation also met the United States Special Envoy on Iran Robert Malley, who leads a US delegation taking part indirectly in the Vienna talks, as well as representatives from China, France, UK, and Germany.

“Zarka went to Vienna to check what is cooking,” a senior Israeli official told the Axios website. “He met everyone other than the Iranians."