BAGHDAD — The United States is now winning the war that two years ago seemed lost.

Limited, sometimes sharp fighting and periodic terrorist bombings in Iraq are likely to continue, possibly for years. But the Iraqi government and the U.S. now are able to shift focus from mainly combat to mainly building the fragile beginnings of peace — a transition that many found almost unthinkable as recently as one year ago.

Despite the occasional bursts of violence, Iraq has reached the point where the insurgents, who once controlled whole cities, no longer have the clout to threaten the viability of the central government.

That does not mean the war has ended or that U.S. troops have no role in Iraq. It means the combat phase finally is ending, years past the time when President Bush optimistically declared it had. The new phase focuses on training the Iraqi army and police, restraining the flow of illicit weaponry from Iran, supporting closer links between Baghdad and local governments, pushing the integration of former insurgents into legitimate government jobs and assisting in rebuilding the economy.

Scattered battles go on, especially against al-Qaida holdouts north of Baghdad. But organized resistance, with the steady drumbeat of bombings, kidnappings, assassinations and ambushes that once rocked the capital daily, has all but ceased.

This amounts to more than a lull in the violence. It reflects a fundamental shift in the outlook for the Sunni minority, which held power under Saddam Hussein. They launched the insurgency five years ago. They now are either sidelined or have switched sides to cooperate with the Americans in return for money and political support.

Gen. David Petraeus, the top U.S. commander in Iraq, told The Associated Press this past week there are early indications that senior leaders of al-Qaida may be considering shifting their main focus from Iraq to the war in Afghanistan.

Ryan Crocker, the U.S. ambassador to Iraq, told the AP on Thursday that the insurgency as a whole has withered to the point where it is no longer a threat to Iraq's future.

"Very clearly, the insurgency is in no position to overthrow the government or, really, even to challenge it," Crocker said. "It's actually almost in no position to try to confront it. By and large, what's left of the insurgency is just trying to hang on."

Shiite militias, notably the Mahdi Army of radical cleric Muqtada al-Sadr, have lost their power bases in Baghdad, Basra and other major cities. An important step was the routing of Shiite extremists in the Sadr City slums of eastern Baghdad this spring — now a quiet though not fully secure district.

Al-Sadr and top lieutenants are now in Iran. Still talking of a comeback, they are facing major obstacles, including a loss of support among a Shiite population weary of war and no longer as terrified of Sunni extremists as they were two years ago.