JERUSALEM—Sheldon Adelson, the U.S. casino magnate who has committed more than $30 million to independent efforts to defeat President Barack Obama, is expected to be among the donors mingling with Mitt Romney at a fundraiser in Jerusalem on Monday.

But the Romney campaign, in a break in the protocol developed between reporters and the campaign months ago, has decided to bar reporters from that event.

The presumed Republican nominee’s campaign opened its fundraisers to a small pool of reporters in May, as long as they were being held in public venues like hotels and restaurants. Those in private homes were deemed off-limits.

But Romney’s travelling press secretary, Rick Gorka, said Saturday that Monday’s fundraiser at the King David Hotel in Jerusalem would be closed. He declined to offer an explanation.

Dan Senor, the senior policy adviser who helped plan the Israel trip, referred questions to Romney headquarters.

Adelson, the billionaire chief executive of Las Vegas Sands, almost single-handedly kept Romney’s one-time rival, Newt Gingrich, in the GOP nominating race by donating more than $21.5 million to Winning Our Future, the “super PAC” that supported the former House speaker.

In June, Adelson directed $10 million to the pro-Romney super PAC Restore Our Future.

Romney arrived in Tel Aviv shortly after 9 p.m. Saturday. He plans to spend nearly all 36 hours of his trip in Jerusalem, meeting with Israeli and Palestinian leaders. He will deliver remarks about the threats facing Israel on Sunday evening near the end of the Jewish holiday Tisha B’av.

After the speech, Romney will attend a traditional fast-breaking meal at the home of Prime Minister Benjamin Netanyahu.

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