A US State Department official on Monday described Iran's restart of nuclear activities as "unfortunate."

The official, who asked not to be named, made his comment safter Iran announced the resumption of uranium conversion work at its Isfahan plant.

"We've said all along that should Iran break the seals and restart uranium enrichment at Isfahan or anywhere else, we would think an appropriate response would be a referral to the United Nations," the official said.

He said that he expected the International Atomic Energy Agency(IAEA) to take an "appropriate action" during a board meeting this week.

Iran resumed uranium conversion activities at its Isfahan nuclear facility Monday after IAEA inspectors finished installing surveillance instruments there. Seals on the equipment were removed.

Iran suspended work at the plant and its other nuclear facilities in November to avoid sanctions and as a gesture in negotiations with the Europeans.

Source: Xinhua