IAEA inspectors have concluded Iran is further along in its nuclear program than believed before, now being able to enrich uranium on a far larger scale than before after solving technological issues.

More troubling, however, is that the IAEA admits they still don’t know a great deal about Iran’s nuclear program.

Inspectors are concerned that Iran has declined to answer a series of questions, posed more than a year ago, about information Iran probably received from Abdul Qadeer Khan, the Pakistani nuclear engineer. Of particular interest is a document that shows how to make uranium into spheres, a shape suitable for use in a weapon.

The IAEA estimates that by June Iran may have 3,000 centrifuges in operation, enough to build one bomb per year, but Iran also plans to expand that amount of centrifuges in the future.