When U.S. Army officers try to explain the challenge of rebuilding Iraq, they often talk about the three different time pieces they’re working with: Washington’s is a stop watch, where every second longer we stay in Iraq is a problem; the Iraqi Shiite-led government’s watch often seems broken, and you have to regularly tap it to get it to work; and the Iraqi Sunni watch always wants to go in reverse – back to Saddam’s day, when Sunnis were in charge.

I’ve just bounced between Baquba and Balad and a Sunni and Shiite neighborhood in Baghdad as an embedded reporter with the visiting Adm. William Fallon, head of the Central Command. I don’t know whether the surge is working – too early, too short a visit. But I did see something new here, which, if played right, could help to stabilize Iraq and better synchronize some of those watches.

It’s this: the willingness of the Sunni tribes, and key Sunni neighborhood leaders in Baghdad, to work side by side with the American soldiers they’ve been shooting at for four years in order to retake Sunni towns and districts from the Taliban-like, pro-Al Qaeda Iraqi Sunnis who took charge in 2006, when the undermanned United States forces pulled out of many areas and handed over security to unprepared Iraqi Army units. Ironically, a key reason violence appears to be trending lower here is because Al Qaeda’s "surge" in 2006 so frightened Iraq’s more moderate, occasionally whisky-drinking Sunni tribal leaders – the backbone of the Sunni community here – that they became willing to work with the Americans just when the U.S. surge was taking off.

Warning! This important shift by the Sunni tribes could come unglued if the Shiite-led Iraqi government doesn’t start providing government services – water, fuel and electricity – to the Sunni areas the tribes have retaken. It could also come apart because, well, this is Iraq. As one U.S. general said to me of the Sunni tribes, "They still hate us. They just hate Al Qaeda even more right now and they hate the Persians even more than them. But they could turn their guns back on us anytime." Baquba, in the heart o

f Diyala Province, north of Baghdad, is a microcosm of what happened. Last March, as the U.S. military was trying to retake this region from Iraqi jihadists – who had declared it the capital of "The Islamic State of Iraq" and imposed a reign terror, including beheadings for un-Islamic behavior, restrictions on women’s dress and a ban on smoking and alcohol – a U.S. intelligence drone picked up fighting between two Iraqi factions inside the city.

The next day, one of those factions, representing local Sunni tribes, asked a U.S. field officer for help in evicting the Islamic extremists. Thus began a cooperative endeavor that now embraces virtually all 25 Sunni and Shiite tribes in the area, and has the U.S. paying the tribes’ sons to be neighborhood patrols in their own towns and villages. As a result, Baquba’s market, which was sealed shut three months ago, was jammed on Sunday with women shopping for cucumbers, tomatoes and figs at different stalls and men making copies of documents at sidewalk Xerox machines. Meanwhile, the U.S. forces also brought the official Iraqi Army back into Baquba – only this time with a new division commander – Maj. Gen. Salim Karim Salih, a respected, retired Sunni Army officer, who was one of Saddam’s top generals in the Iran-Iraq war and whose home was nearby. He, too, was ready to work with the Americans to get rid of the pro-Al Qaeda Iraqis. "The citizens asked me to come back," he told me. "We need a political solution. But the politics has to be impartial and not just favor one side. And we need action not more words." That is code for the Shiite-led central government sending money to help repair the town, which it has started to do. "We are in a disaster state now," added the governor of Diyala Province, Ra’ad al-Tamimi. "We hope the central government will interact with us in a better way."

I understand the Shiite’s reticence. The Sunnis have resisted everything for four years and now they want government services. But it is in our interest, because it increases the chances of the only possible solution here, and that is a loose federation in which each sect controls its own areas and Baghdad serves as an oil-funded A.T.M., dispensing cash proportionally.

That is the only way we can get out of here without Iraq exploding. Or, as a Kurdish official said to me: "If you wanted a united Iraq, you never should have gotten rid of Saddam, because he was the only one who could hold this place together."