Baghdad, Iraq ? He is virtually unknown to most Americans. Yet since the day of the Sept. 11 attacks, Zalmay Khalilzad has handled some of his country’s most-delicate diplomatic assignments.

Now, the man known at the White House and CIA as just “Zal” takes on his biggest challenge – running America’s relations with Iraq. As he does, Khalilzad may be forced to scale back the high profile he held as ambassador to Afghanistan, where he met the Afghan president so often that some believed he virtually ran the place.

But Khalilzad, who started his new job Saturday at meetings with Iraq’s president and prime minister, shows no signs of shrinking from sight.

“Iraq is different than Afghanistan, and Afghanistan is different from Iraq – but I am the same person,” Khalilzad said just before heading to Baghdad. “I know the Iraqi leaders and they know me … If they need my help, I’m going to be available no matter what time it is of the day.”

Apparent proof of his words came Saturday, when Iraqi President Jalal Talabani greeted him as “our old, dear friend” then closed the meeting with a warm embrace.

In one sign Khalilzad has few plans to give up control, he takes the Iraq job even while retaining his title as President Bush’s special envoy to Afghanistan – in effect, making him the point person on America’s two top overseas hot spots.

Yet Iraq is definitely different, with a new government sensitive on the topic of U.S. military occupation and political influence. Already this week, one prominent Iraqi Kurd accused U.S. officials of interfering in the constitution-drafting process.

“I think he knows Iraq isn’t Afghanistan and that his profile has to be different,” said Anthony Cordesman, an Iraq expert at the Center for Strategic and International Studies in Washington.

Nevertheless, Khalilzad already has pushed hard on the constitution, calling its completion by an Aug. 15 deadline vital. He also plans to plunge into another sensitive topic – talks over eventually reducing U.S. military forces here.

Another priority will be improving U.S. reconstruction aid, now widely viewed as lagging and leaving Iraqis demoralized.

“My approach will be to under-promise and over-deliver,” Khalilzad said Saturday.

Even while busy with Afghanistan, Khalilzad had a hand in Iraq.

Before the U.S.-led invasion to topple Saddam Hussein in March 2003, Khalilzad was a special envoy to the Iraqi opposition.

One of the trickiest issues he will face now is coordinating U.S. diplomatic and aid efforts with U.S. military actions in Iraq.

In Afghanistan, Khalilzad had good relations with the military, said Cordesman.

“He has studied military tactics and counterinsurgency operations, but I don’t think this is someone who sees himself as a commander,” Cordesman said. “This is someone who sees himself as a stimulator.”

– Associated Press reporters Daniel Cooney in Kabul, Afghanistan, and Katherine Shrader in Washington contributed to this report.