Here is Benjamin Netanyahu on Fox News with Chris Wallace: 

when the president [of the United States] says that he's determined to prevent Iran from developing nuclear weapons and that all options are on the table, I think that's the right statement of policy. ...the president's position that all options are on the table might actually have the only real effect on Iran...—if they think it's true.

But do the Iranians think it’s true?

Here, from an interview with David Sanger of the New York Times in late June, is Admiral Mike Mullen, chairman of the Joint Chiefs of Staff, on the prospect of using force to stop Iran from getting nuclear arms.

I've still said this many times and I would repeat it: I still think it is incredibly dangerous for them to achieve this capability, destabilizing in the region. I think it generates the great potential for a nuclear arms race in the Middle East. The place is unstable enough; we don't need that. And at the same time, I think, you know, a strike against Iran also will be, should something like that occur, incredibly destabilizing [emphasis added].

And here is Mullen on the Charlie Rose Show last year.

What I worry about . . .in terms of an attack on Iran, is in addition to the immediate effect, the effect of the attack. It's the unintended consequences. It's the further destablization in the region. It's how they would respond. We have lots of Americans who live in that region who are...under the threat envelope right now, capability that Iran has across the gulf. So I worry about the responses and I worry about it escalating in ways that we couldn't predict. So that kind of option generates a much higher level of risk in terms of outcomes in the region and it really concerns me.

The West has three major pathways to stop Iran's nuclear program: sanctions, the threat of force, and the actual use of force. Time is fast running out on the first option. The second would be greatly preferable to the third. But every time Mullen wrings his hands about the "destabilizing" consequences of a strike against Iran, he diminishes the pressure on Tehran.

The broader consequences of a strike are important to take into account, but Mullen (and Mullen is not alone, for Secretary of Defense Robert Gates has also been chiming in with similar statements) is wrong in constantly harping on them and essentially signaling to the Iranians that we won't strike and we'll counsel the Israelis not to strike. Netanyahu, on the other hand, is on the mark.