TSR: "None of this is unrelated."

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WOLF BLITZER: In Iraq, meanwhile, a car bomb killed at least 15 people on a busy shopping street in Baghdad, just as the defense secretary, Robert Gates, was visiting another part of the city. And those who know the situation there say the overall violence is intertwined with the tense relationship between the United States and Iran.

And joining us, now, from Baghdad, our correspondent Michael Ware.

We know this National Intelligence Estimate now saying that the Iranians actually stopped building a nuclear bomb back in 2004.

But what about these conflicting reports that we're getting about Iran still meddling in Iraq?

What's going on?

MICHAEL WARE, CNN CORRESPONDENT: Well, Wolf, what I can tell you is the latest that U.S. military intelligence is telling Secretary of Defense Robert Gates on his sixth visit here to Iraq. What they're saying is that the number of attacks that they can directly link to Iranian support is down. Whether they can attribute that to a downturn in Iranian influence, that they cannot answer.

The other thing I can tell you: Iranian nuclear issues and Iranian issues on attacks on America here in Iraq are not unrelated.

Now, during the historic talks between the Iranian ambassador here in Iraq and the American ambassador, Ryan Crocker, here in Iraq, it was made very clear they would only talk Iraq. They would not talk nuclear issues or anything else.

Iran's strategy has been to force to America to bleed here in Iraq to gain concessions elsewhere. Indeed, we got to a point where top American commanders were saying just a few months ago, more American troops were dying as a result of Iranian-backed violence than Al Qaeda-backed violence. We've now seen that dip.

But right now, I can tell you, Secretary Gates is being told that Iran, according to U.S. military intelligence, is still training Iraqis to kill Americans. None of this, Wolf, is unrelated.

BLITZER: Robert Gates -- he's in Baghdad right now -- an unannounced visit. And he and others are suggesting things clearly are getting better.

Is security and stability in Iraq right now within reach?

WARE: The short answer is that, yes, things are better. Where we would have 1,500 or 1,600 attacks a week -- be it bombs or shootings or suicide detonations or whatever you want -- it's down to something like 500 on a week.

Can you imagine if there was 500 and something attacks in Pakistan or Israel or America?

Yet this is our idea of success now. That's how numbed we've become to the violence. Nonetheless, less Americans, less Iraqis are dying. There's two reasons for that. One, America is backing Sunni militias. They're protecting their areas. America has finally cut a deal with the insurgency.

Secondly, Iran has cut down its military activity. You talk to the top U.S. officials, they don't yet know why. They don't believe it will hold. But there's a key question there. It's quite a dilemma -- Wolf.

BLITZER: Michael Ware, our reporter in Baghdad.

Michael, thanks.

WARE: Thank you, Wolf.

It's a pleasure.