The United States went through its own transition in Iraq yesterday, as the end of the Pentagon-dominated Coalition Provisional Authority also marked the transfer of authority for dealing with Iraq to the State Department.

The relief could almost be felt along State Department corridors after nearly two years of sporadic but bitter tension with the Pentagon. Career diplomats in charge of crafting foreign policy often grumbled about being marginalized or vetoed on Iraq policy by political appointees at the Defense Department.

"Clearly, the Department of State is taking the lead now. We will be the dominant voice," Deputy Secretary of State Richard L. Armitage told National Public Radio within hours of the political handover.

The shift is reflected in the personnel changes. For the past 14 months, U.S. administrator L. Paul Bremer reported to the Pentagon; the new U.S. ambassador to Iraq, John D. Negroponte, who will head the largest U.S. embassy in history, will report to the State Department.

State Department officials blame many of the problems during the 14-month occupation on disarray within the U.S.-led coalition, inexperience by young staffers in key positions and the military's lack of preparedness to run Iraq after the fall of Saddam Hussein.

"The CPA was a hybrid of military and Pentagon officials, outside contractors, Foreign Service officers and people from all over the government. There was no common culture, and it had an impact on how the system worked," said a senior State Department official with experience in Iraq. "A lot of the chain-of-command issues were unclear."

He declined to be identified under department rules limiting who may speak on the record.

State Department officials say policy had to be salvaged time and again with what they describe as last-minute "audibles" during crises or challenges -- referring to a football term to describe changes in a play called by the quarterback on the field.

"The broad difference is that we regard this as our core business. We're used to dealing with this kind of complex political situation. That doesn't automatically mean we'll be more successful, but at least we have the structures in place to deal with it," the senior State Department official said.

Despite the enormous obstacles looming in the months ahead, State Department officials were predicting yesterday how much better things will work in Baghdad -- for U.S. officials as well as Iraqis.

"There's a sense at State that the U.S. Embassy is now stood up and we're going to get it right. We have a new relationship with the [Iraqi] government, and it's going to work. We've learned a lot of lessons over the past year, and this allows us to turn over a new leaf and act on the basis of what we've learned," said another senior U.S. official familiar with Iraq policy who asked to remain anonymous because of government rules. "We're not going to fail."

State Department deputy spokesman J. Adam Ereli told reporters, "The U.S. Embassy will hit the ground running."

As during the occupation, the process will still be heavily driven by the White House, although now through a State Department prism, officials said. The Pentagon will still have a major role because of the roughly 140,000 U.S. troops likely to remain in Iraq for months, although it will adopt a lower profile, they added.

In the aftermath of showdowns in Fallujah and with the militia of radical Shiite cleric Moqtada Sadr, "military commanders will now be much more circumspect, much more restrained about undertaking actions," a senior U.S. official said.

The overall mission will also change, as the new U.S. Embassy focuses more on reconstruction now that Iraqis have assumed control of the political transition. After a lengthy battle, the State Department has wrested jurisdiction over the specifics of how about $18 billion allocated for general projects by Congress may be spent, although the Pentagon will continue to administer and manage the funds.

In Washington and Baghdad, U.S. officials stressed that American diplomats and troops will play only a support role.

"It is now our job to support this government and the democratic aspirations of the Iraqi people as they work to secure their country against those who seek to turn the clock back, and as they work to establish a functioning democracy and a fully representative government that is chosen by all of the people through free and fair elections," Ereli told reporters.

As part of the surprise early transfer of political authority, the United States had to hastily arrange for Negroponte to get to Baghdad within hours after Bremer's exit. But the transfer was happening so fast -- and abruptly -- that even the State Department seemed not to be able to keep up.