WASHINGTON—Supreme Leader Ayatollah Ali Khamenei has decided to keep Iran's nuclear program within limits demanded by Israel for now, according to senior U.S., European and Israeli officials, in a move they believe is designed to avert an international crisis during an Iranian election year.

With a vote set for June, Mr. Khamenei is eager to place a leader more aligned with his positions than current Iranian President Mahmoud Ahmadinejad, without sparking a repeat of the nationwide unrest that followed a 2009 vote, these officials...