Iran ? In an unusually frank disclosure, Iran’s nuclear chief said Tuesday the country’s new uranium enrichment site was built for maximum protection from aerial attack: carved into a mountain and near a military compound of the powerful Revolutionary Guard.

Iran’s revelation that it covertly built a second uranium enrichment plant has raised international concerns that other secret nuclear sites might exist as well.

Iranian nuclear chief Ali Akbar Salehi’s statement came with a hard-line message ahead of crucial talks this week with the U.S. and other world powers: Iran will not give up its ability to produce nuclear fuel.

The details emerging about the secret site near the holy city of Qom have only heightened suspicions that Iran is trying to build a nuclear bomb, despite repeated denials.