In an interview with Newsweek magazine published Thursday, Bruce Riedel said that he talked to defense officials and to officials in the Mossad, or Israeli secret service, during a recent visit.
"I came back from a trip to Israel in November convinced that Israel would attack Iran," Riedel said. "And that was before the NIE. This makes it even more likely. Israel is not going to allow its nuclear monopoly to be threatened."
The National Intelligence Estimate said that Iran had abandoned its nuclear weapons development program in 2003. While some in the administration have questioned the report, its release suggests that the Bush administration is unlikely to consider military action.
Ephraim Sneh, a member of the Israeli parliament and former deputy defense minister, told Newsweek that he has believed for a long time that Israel would have to deal with Iran single-handed.
"Today we are closer to this situation than we were three weeks ago," he said. " We have to be prepared to forestall this threat on our own."