An Obama administration assessment of the Iran nuclear deal provided to Congress has led a number of lawmakers to conclude the U.S. and world powers will never get to the bottom of the country’s alleged efforts to build an atomic weapon, and that Tehran won’t be pressed to fully explain its past.

In a report to Capitol Hill last week, the administration said it was unlikely Iran would admit to having pursued a covert nuclear weapons program, and that such an acknowledgment wasn’t critical to verifying Iranian commitments in the future.

Details of the report, which haven’t been previously disclosed, indicate the deal reached this month could go ahead even if United Nations inspectors never ascertain conclusively whether Iran pursued a nuclear weapons program—something Tehran has repeatedly denied.