Pay very close attention to this story because it has important implications for both Israel and Iran. In Tel Aviv today, Chairman of the Joint Chiefs of Staff Adm. Michael Mullen walked a fine line between support for Israel and support for a military strike. While some columnist will inevitably bemoan the U.S. "acceptance" of a nuclear Iran (UPDATE: JPost doesn't disappoint), Mullen's comments are well thought out and are critical to the success of a new round of sanctions...and preventing Iranian nuclear capability.
Mullen's ability to appear reticent to give Israel and amber light to strike Iran is critical to U.S. strategy for two reasons. Firstly, Iran must think that the U.S. can, if its demands are met, prevent an Israeli military strike. The ability of the U.S. government to hold Israel back are one of the few carrots the U.S. has to offer Iran. Mullen's visit is a demonstration that should Iran choose to cooperate, it will be rewarded with a stronger security posture.
Secondly, it is important for the U.S. to avoid pulling an "April Glaspie" and send mixed signals about its intentions. If Iran becomes convinced that a U.S. or Israeli strike is imminent, despite other messages to the contrary, it has no incentive to continue engaging in diplomacy (see Gulf War, The First). Mullen can't say that he supports an Israeli military strike because it would completely undermine U.S. efforts, including the new round of targeted sanctions issued by the Treasury last week.
That being said, while Mullen is not offering an amber light to Israel, his visit in and of itself is intended as a show of strength of the U.S. - Israel military relationship. This sends a clear signal to Iran, but also to the people and government of Israel. Military cooperation is the most obvious nexus of cooperation between the U.S. and Israel, and Mullen's visit is a strong signal that despite the row over settlements, this crux of the relationship is stronger than ever.
Mullen's visit to Israel has thus far been a textbook example of compellance strategy, and the message from the U.S. to Iran is crystal clear: A military strike is not inevitable, but you'd better act soon.