The U.S. on Friday demanded that Iran confess to trying to make atomic weapons, suggesting that anything short of that would doom an International Atomic Energy Agency probe of Tehran’s nuclear past, reported AP from Vienna.

The call by Gregory L. Schulte, chief U.S. delegate to the Vienna-based IAEA, appeared to set the bar insurmountably high for the investigation by the U.N. agency’s chief, Mohamed ElBaradei.

Schulte said the “measure for progress is whether Iran fully discloses its past weapons work and allows IAEA inspectors to verify it’s halted.”

“This,” he told reporters, “includes explaining past work on weapons design and weaponization and the role of the Iranian military