(CNN) -- Osama bin Laden's release of an audio message denouncing Israel's military offensive in Gaza signals the al Qaeda leader's priorities, CNN national security analyst Peter Bergen says.

Peter Bergen says Osama bin Laden releases few messages because they open him up to detection.

On the tape, which became public Wednesday, bin Laden calls for jihad, or holy war, against Israel in response to its military campaign aimed at stopping Hamas rocket attacks.

It's unknown when the tape was made because the time lag between recording a bin Laden message and releasing it is usually about two weeks, said Bergen, a fellow at the New America Foundation in Washington and author of "The Osama bin Laden I Know: An Oral History of al Qaeda's Leader."

Bergen answered questions about the latest message from bin Laden.

Q: When was the last time we heard from bin Laden?

Peter Bergen: We haven't heard from him in nine months. We were expecting to hear from him during the run-up to the presidential election, as we had four years ago in the previous presidential election, and heard nothing. Watch why Bergen thinks bin Laden remains relevant »

This is a long period for him not to have said anything, and one potential reason is that by our bureau in Pakistan's count, there have been 30 Hellfire missile strikes into the tribal zones in Pakistan in the last year, whereas in 2007 there were only four.

Those Hellfire missile strikes put pressure on al Qaeda and killed a number of key leaders in the last several months. In fact, President Bush referenced those strikes in an interview [Tuesday] night with Larry King -- two al Qaeda leaders killed January 1.

The missile strikes have gone up exponentially in the last year, and clearly that's going to put a crimp on al Qaeda's activities. He's survived, but these airstrikes have clearly been highly interruptive.

Q: Why are we hearing this time from bin Laden and not his lieutenant, Ayman al-Zawahiri, who speaks out much more frequently?

Bergen: [Al-Zawahiri] has been releasing more videotapes, and there's been an occasion when [al-Zawahiri's] released two tapes in one week. Hearing from [al-Zawahiri] is no longer a newsworthy event.

Bin Laden has been a lot more careful.

The obvious reason for this is that with the release of a videotape or audiotape, you're opening yourself up to detection. Somebody's got to tape the thing, and somebody's got to take it to either the Al-Jazeera bureau or, more generally, a jihadi Web site. There's a chain of custody, and every time you do this you open yourself to exposure.

So I think they've just made the calculation that Ayman al-Zawahiri's going to be more talkative and that bin Laden is more important, and he's not going to say much unless it's sort of a big deal. And the Israeli attacks on Gaza would certainly be a big deal for bin Laden.

If we hadn't heard from him at all in all of this, I think it would have been very puzzling.

Q: Does the timing of the message seem to be affected by the impending inauguration of Barack Obama as president?

Bergen: I think it's affected by the Gaza issue. The Israeli-Palestinian issue is something bin Laden has been pretty vocal about for more than a decade. It's nothing specifically to do with the inauguration.

I'm pretty sure he doesn't care whether it's President Obama or President Bush. In the early '90s, they were using a picture of President Clinton for target practice.

There's going to be no substantially different Obama administration policy on most of the issues bin Laden cares about. I mean, he wants the destruction of the state of Israel. Obviously the Obama administration is not going to advocate that.

Q: Is bin Laden still relevant? Do people still listen and respond to him?

Bergen: I think if he were irrelevant, we wouldn't be doing the coverage.

He's less relevant than he might have been a few years ago because a lot of Muslims have turned against al Qaeda because of its tactics and suicide operations. But there are clearly people who still think he's important.

He can put out general messages, you know, inciting people to violence, and this is the way it happens. So he puts out the strategic guidance to al Qaeda, through the jihadi network, through the audio and videotapes.

Sometimes he makes specific calls for attacks on particular places. For instance, he called for attacks on Spain, and there were attacks in Madrid in 2004. He called for a response to the Danish cartoons of the Prophet Mohammed, and there was an attack by al Qaeda on the Danish Embassy in Pakistan last year. And I can give you several other examples.

That's the way he maintains operational control.

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