VIENNA (Reuters) - The head of the U.N.’s nuclear inspectorate has undergone an unspecified medical procedure and will not return to Vienna, where the agency is based, for roughly a month, it said on Thursday.

FILE PHOTO: International Atomic Energy Agency (IAEA) Director General Yukiya Amano waits for the start of a board of governors meeting at the IAEA headquarters in Vienna, Austria June 4, 2018. REUTERS/Leonhard Foeger/File Photo

Yukiya Amano, a 71-year-old Japanese diplomat, was last year reappointed to a third four-year term in charge of the International Atomic Energy Agency. Its responsibilities include policing restrictions placed on Iran’s nuclear activities under the country’s 2015 deal with world powers.

Amano “has undergone a medical procedure outside Austria. The procedure was successful and he is making steady progress toward full recovery,” the IAEA said in a statement.

The IAEA did not say where Amano had been treated or what he had been treated for.

“Director General Amano continues to discharge his responsibilities, supervising and guiding the work of the agency in close communication with his office,” the IAEA said.

“He is also overseeing the preparations and provides guidance to senior IAEA staff for these meetings. He is expected to return to Vienna in early October.”.

Amano’s treatment comes at a sensitive time, since the U.S. announced its withdrawal from the Iran accord in May and the reimposition of sanctions that were lifted under that agreement. Some of those have already taken effect and others are due to come into force in November.

Despite efforts by European powers to shield companies and protect Iranian oil revenues and other sources of income, many diplomats and analysts believe the deal could soon fall apart, prompting Iran to ramp up atomic activities beyond caps imposed under the accord.

Amano will also miss one of the busiest periods of the year for his agency. In addition to a quarterly meeting of its 35-nation Board of Governors next week, it is due to hold an annual meeting of all its member states the following week.

Amano’s absence also follows the sudden resignation in May of the head of the IAEA department in charge of inspections, one of its most sensitive activities.

The IAEA said earlier on Thursday that the news conference Amano normally holds on the first day of the Board of Governors meeting would not take place. It did not say why.