Iran ? Iran pressed ahead Monday with plans that will increase its ability to make nuclear weapons as it formally informed the U.N. nuclear agency of its intention to enrich uranium to higher levels.

Alarmed world powers questioned the rationale behind the move and warned the country it could face more U.N. sanctions if it made good on its intentions.

Iran maintains its nuclear activities are peaceful, and an envoy insisted the move was meant only to provide fuel for Tehran’s research reactor. But world powers’ fears that Iran’s enrichment program might be a cover for a weapons program were critical.