BAGHDAD, April 8 — The convoy chugged into the mosque today with signature black Shiite flags flapping from the pickup trucks. Carried in back were sacks of grain, flour, sugar and rice. And gallons of tomato juice, crates of oranges, vats of cooking oil and boxes of powdered milk.
Though the food donations were coming from Shiite families, and in many cases poor families with little to spare, the collecting point was a Sunni mosque. And though Shiite holy men were the ones organizing the food drive, the recipients were the besieged residents of Falluja, a city in the heart of the Sunni triangle that has now become an icon of resistance.
"Sunni, Shia, that doesn't matter anymore," said Sabah Saddam, a 32-year-old government clerk who took the day off to drive one of the supply trucks. "These were artificial distinctions. The people in Falluja are starving. They are Iraqis and they need our help."
But it is not just humanitarian aid that is flowing into the city.
According to several militia members, many Shiite fighters are streaming into Falluja to help Sunni insurgents defend their city against a punishing Marine assault. Groups of young men with guns are taking buses from Shiite neighborhoods in Baghdad to the outskirts of Falluja and then slipping past Marine checkpoints to join the battle.
"We have orders from our leader to fight as one," said Nimaa Fakir, a 27-year-old teacher and foot soldier in the Mahdi Army, a Shiite militia. "We want to increase the fighting, increase the killing and drive the Americans out. To do this, we must combine forces."
The Falluja situation represents an emerging level of Shiite-Sunni cooperation unheard of in the year-old occupation and maybe even the modern history of Iraq. Saddam Hussein exploited divisions between the two sectarian groups. So did many other Iraqi leaders. When American soldiers invaded the country a year ago, preventing a civil war between Shiites, who make up the majority, and Sunnis, who used to hold all the power, was one of the Bush administration's chief concerns.
But now that the resistance is heating up, spreading from town to town, the Sunnis and Shiites are drawing together. American military leaders say they have been watching closely.
"The danger is we believe there is a linkage that may be occurring at the very lowest levels between the Sunni and Shi'a," Lt. General Ricardo Sanchez, commander of the occupation forces, said today. "We have to work very hard to ensure that it remains at the tactical level."
He also said the call for unity is "clearly an attempt to take advantage of the situation."
While fighting is now heavy in many places, Falluja has become the resistance's rallying cry.
The city, 35 miles west of Baghdad, is its fifth day of siege. Marines are trying to root out insurgents after four American security guards were ambushed there last week and their bodies mutilated and dragged through the streets. According to people inside Falluja, the situation is grim and getting grimmer.
"It's a disaster," said Sheik Ghazi Al Abid, a wealthy tribal leader. "There's no food, no water and no electricity."
The sheikh said it was so dangerous, bodies have been left on the streets because the people are terrified to venture outside to collect them.
"We need all the help we can get," the sheikh said.