Israel appears to be preparing to launch an attack soon on Iran, according to officials in the United States and Europe, a step that could further inflame the Middle East and derail or delay efforts by the Trump administration to broker a deal to cut off Iran’s path to building a nuclear bomb.

The concern about a potential Israeli strike and the prospect of retaliation by Iran led the United States on Wednesday to withdraw diplomats from Iraq and authorize the voluntary departure of U.S. military family members from the Middle East.

It is not clear how much effort Mr. Trump made to block Mr. Netanyahu again this time, but the president has appeared less optimistic in recent days about the prospects for a diplomatic settlement after Iran’s supreme leader rejected an administration proposal that would have effectively phased out Iran’s ability to enrich uranium on its soil. Mr. Netanyahu has walked up to bombing Iran’s nuclear facilities in the past, only to back off at the last minute.