IAEA Director General Grossi speaks with journalists in central Kyiv
IAEA Director General Rafael Mariano Grossi speaks with journalists amid Russia's invasion of Ukraine, in central Kyiv, Ukraine October 13, 2022. Reuters

International Atomic Energy Agency (IAEA) chief Rafael Grossi expects to return "soon" to Ukraine, he told Reuters on Tuesday, amid negotiations to establish a security protection zone around the Russian-occupied Zaporizhzhia nuclear power plant.

Grossi has been the go-between from Moscow to Kyiv in an effort to establish a nuclear safety and security protection zone around the plant, which has been hit by power outages in the past weeks due to shelling of the site.

Earlier, the IAEA said it was deeply concerned by the detention of two Ukrainian staff from the Zaporizhzhia plant, which is in one of four Ukrainian regions Russia has proclaimed as annexed but only partly occupies.

"There is a possibility I will return to Ukraine and Russia, it is in fact what we have agreed in principle, at this moment we are continuing the consultations aimed at establishing the protection zone," he told Reuters during a trip to Argentina.

"This implies an interaction where I receive answers and reactions from the two sides and I am looking for new ways to move forward and for that, at some point, probably very soon I will have to return."

The talks are seen as key to defusing concerns that have mounted since August about the risks of shelling at or near Zaporizhzhia, Europe's largest nuclear power station. Russia and Ukraine have both blamed each other for the shelling.

The head of the IAEA, the U.N. nuclear watchdog, said that separate Russian threats to use nuclear weapons in Ukraine could not be ruled out but that it was "not an immediate possibility".

"I believe that the possibility of Russia using nuclear weapons is not an immediate possibility. Obviously nothing can be ruled out, I am not in the decision-making mechanism of that country, but I believe that it would be an extreme measure," he said.

Grossi, asked about ongoing talks to revive an Iran nuclear deal, said that the negotiations were at a "stalemate", adding that the IAEA lacked key information due to restriction on access to inspections in recent months.

The United States last week said that reviving the 2015 Iran nuclear deal was "not our focus right now", adding Tehran had showed little interest in reviving the pact and that Washington was concentrating on how to support Iranian protesters.