The counterpunch coincides with preparations by U.S. and Iraqi forces for an offensive in the northern city of Mosul, described as al-Qaeda in Iraq's last urban stronghold.

American commanders and diplomats have been careful in their assessments of the recent downturn in violence in Iraq - routinely saying that al-Qaeda in Iraq is on the run but not defeated. Its resurgence in recent days gave strength to those caveats.

Its resiliency began showing itself Feb. 1, when two women with Down syndrome were strapped with explosives then detonated by remote control minutes apart in two Baghdad pet markets. The final death toll was 99.

In the meantime there have been a series of hit-and-run bomb attacks countrywide, with most of the victims being Sunni tribesmen who have turned against al-Qaeda and are now fighting alongside American and Iraqi soldiers.

It happened again yesterday when twin car bombs targeted a meeting of U.S.-allied Sunni tribal leaders in Baghdad, killing as many as 22 civilians and wounding 42, according to police and hospital officials who spoke on condition of anonymity because they were not authorized to disclose the information.

Brig. Gen. Qassim al-Moussawi, the top military spokesman for Baghdad, said an explosives-laden minibus and a sedan blew up minutes apart - the first near a gas station and the second near the tribal chiefs' meeting place about half a mile away. The Anbar sheikhs often meet in Baghdad.

"There is no question," said Rear Adm. Gregory Smith, a U.S. military spokesman, "that [al-Qaeda in Iraq] has sought to respond to the recent offensive operations launched by Iraqi and coalition forces by striking soft targets, killing innocent civilians, and interrupting essential services."

Yesterday began with an explosion at dawn along a major natural-gas pipeline that serves power-generating stations in Beiji, Kirkuk, and other urban areas in the north and northeast.

Electricity Minister Karim Waheed told the Associated Press the power would not be back to normal in the north of the country for at least a week.

A truck bomb Sunday also took out a key generating plant in Mosul, he said.

"If there is no security or political stability," Waheed said, "there is no way I can promise the Iraqi people that the electricity sector will improve in the coming years."

The country's national grid frequently breaks down as a result of sabotage, and many cities in the south have taken their local networks out of the national system, meaning that power stations in those locations are not sharing generating capacity.

Baghdad residents and many urban dwellers elsewhere are used to living without national power, which is on just a few hours a day at best. Those who can afford the alternative have private generators or are wired into private neighborhood generating systems.

But gasoline and diesel-fuel prices have risen to the point where many, if not most, people simply do without electricity.