The Biden administration expects a restored nuclear deal would leave Iran capable of amassing enough nuclear fuel for a bomb in significantly less than a year, a shorter time frame than the one that underpinned the 2015 agreement, U.S. officials familiar with the matter said.

Administration officials concluded late last year that Iran’s nuclear program had advanced too far to re-create the roughly 12-month so-called breakout period of the 2015 pact, the U.S. officials said.