PARIS (Reuters) - Iran risks triggering a new crisis if it does not cooperate with the U.N. nuclear watchdog after failing to answer its questions about past nuclear activities at three sites and denying it access to two of them, its chief said on Tuesday.

FILE PHOTO: International Atomic Energy Agency (IAEA) Director General Rafael Grossi gestures during an interview with Reuters in his office in Vienna, Austria December 3, 2019. REUTERS/Leonhard Foeger/File Photo

Rafael Grossi, who took up his post in December, spoke to Reuters in an interview hours after he and the International Atomic Energy Agency (IAEA) he heads released a report admonishing Iran.

“We have been requesting some information and access from Iran but we haven’t been getting the information we require,” he said.

“We have insisted and despite all our efforts we have not been able to get that, so the situation requires on my part such a step because what this means is that Iran is curtailing the ability of the agency to do its work.”

Reuters first reported on Monday that the IAEA planned to issue a second report in addition to its regular quarterly update on Iran’s nuclear activities, rebuking Iran for less than full cooperation in general and for failing to grant U.N. inspectors access to one or more sites of interest.

Speaking after meetings in Paris, including with French President Emmanuel Macron, Grossi said the issue was serious and he hoped that Iran would return to full compliance after the IAEA’s board of governors meets in Vienna next week.

“I sincerely hope that Iran will listen to us and listen to the voice of the international community at the board of governors and assess that it is in their own interest to cooperate with us,” he said. “We don’t have a political agenda; we simply are requesting them to comply with their obligations.”

“We will be walking towards a crisis (if not),” he said.

The extraordinary second report delved into the IAEA’s open questions and Iran’s denial of access to sites which diplomats say are believed to have been active in the early 2000s.

“I judged it necessary to produce a second report because I thought the situation is serious enough to merit such a move on my part,” Grossi said.

What exactly is thought to have happened at the three sites, none of which the IAEA has visited before, is unclear and in Tuesday’s report Iran said it had informed the IAEA that it would not recognize any allegation on past activities and did not consider itself obliged to respond.

“These sites have been judged by our technical experts as indispensable for us to visit to provide the necessary guarantees that nothing is happening which shouldn’t be happening there.” Grossi said.