The top U.S. military officer admitted on Wednesday he did not know whether Israel would alert the United States ahead of time if it decided to take military action against Iran.

In an interview with the Reuters news agency, General Martin Dempsey, the chairman of the Joint Chiefs of Staff, also acknowledged that there are differences in perspective between the United States and Israel over the best way to handle Iran and its nuclear program.

Dempsey said the United States was convinced that using sanctions and diplomatic pressure was the right path to take on Iran, along with “the stated intent not to take any options off the table.”

He said, however, “I’m not sure the Israelis share our assessment of that. And because they don’t and because to them this is an existential threat, I think probably that it's fair to say that our expectations are different right now.”

When asked whether he was talking about the differences between Israeli and U.S. expectations over sanctions, or differences in perspective about the future course of events, Dempsey said “all of the above” but would not elaborate.

He did not disclose whether he believed Israel was prepared to strike Iran, and when asked directly whether Israel would alert the United States ahead of time if it chose to go forward with military action, Dempsey replied: “I don't know.”

It has been widely speculated in recent weeks that Israel may launch an attack on Iran’s nuclear facilities.  These speculations have grown in the wake of a recent report by the International Atomic Energy Agency (IAEA), which said the agency had credible intelligence Iran is seeking nuclear weapons technology.

Israeli officials have mostly chosen to keep quiet and not directly say whether Israel is indeed planning such an attack, but Israel's media and former officials are holding heated debates on the subject. Defense Minister Ehud Barak recently told CNN that a military strike on the Islamic Republic is not “a subject for public discussion.” Israel’s official position on the issue is that all options are on the table.