LONDON — The Obama administration’s successful push for an accord that would temporarily freeze much of Iran’s nuclear program has cast a spotlight on the more formidable challenge it now confronts in trying to roll the program back. For all of the drama of late-night make-or-break talks in Geneva, the deal that Secretary of State John Kerry and his negotiating partners announced early on Sunday was largely a holding action, meant to keep the Iranian nuclear program in check for six months while negotiators pursue a far tougher and more lasting agreement. By itself, the interim pact does not foreclose either side’s main options or require many irreversible actions — which was why the two sides were able to come to terms on it. That was also a reason for the sharp negative reaction the deal elicited on Sunday from Israel, an American ally that is deeply suspicious of […]