Until recently, the people of Sadr City and Adhamiya dared not enter each other's neighbourhoods, even though their two districts are on the same side of Baghdad. Today, they are sharing their food, their feelings and their very blood.
Sadr City, a sprawling slum in the north of Baghdad, is peopled by poor Shias who were oppressed by Saddam Hussein's Sunni-dominated Ba'athist regime. The neighbourhood was therefore only too happy when US forces overthrew the president last year.
Nearby is Adhamiya, a Sunni and Ba'athist stronghold and, as home to many of Saddam's diehard supporters, the target of many US raids. Its people used to consider themselves superior, calling their Shia neighbours "animals" and "beasts". Now, everyone feels they have a common link: the US-led occupation.
"All the people of Iraq - Sunni, Shia, Kurd - are united now," said Daoud al-Akoubi, 44, a Shia from Sadr City, as he sat outside his home staring glumly across the street, observing the damage to the local office of the firebrand Shia cleric Moqtada al-Sadr, which US forces recently attacked.
As al-Akoubi surveyed the damage, he said he sympathised with the Sunnis of Fallujah, a former Ba'athist stronghold that US forces have vowed to pacify after the brutal killing of four American security contractors and the desecration of their bodies a few weeks ago. He pointed out that many people from Sadr City were frequenting Adhamiya, where food and supplies were being collected for the people of the besieged city of Fallujah.
Cars line up daily outside the Abu Hanifa mosque in Adhamiya as donors queue to drop food while others prepare to drive to Fallujah. Enormous piles of food fill the mosque's courtyard - tins of cooking oil and bags of rice, beans, lentils, pasta, sugar and potatoes. A convoy of supplies to Fallujah carried banners saying: "To the people of Fallujah from the citizens of Sadr City".
"Every Iraqi family, Shia and Sunni, is bringing half of what it possesses in its house," said Armiyeh Shaker, a veterinarian who volunteered to manage the collection and distribution. "People are coming from Sadr City and Kadhimiya," he said, listing two Shia areas. "There is no difference. We are all Muslim." Despite the occupation, he said, "We want to thank Bush and America very much for one thing: this pressure has caused the people of Iraq to come together."
That was evident last Friday at the Sunni Um al-Qura, as Shias joined Sunnis - some for the first time in their lives - in a show of solidarity at the midday prayer. Normally, Sunnis and Shias pray in separate mosques. Although it is the largest mosque in Iraq, the Um al-Qura could not accommodate the busloads of worshippers from all parts of the capital who streamed in past the numerous armed mosque security guards, filling the carpeted house of God and the grass grounds around it. Hundreds of men sitting outside listened to the sermon from loudspeakers calling upon them to unite against the US-led coalition.
"We need unity between the Sunnis and Shias against the occupation because the occupation destroys Islam," called the prayer leader, as flyers were passed out with pictures of wounded children and dead bodies lying in the streets of Fallujah. "The occupation has not benefited Iraq at all," he said. Standing in rows, side by side, the blossoming brotherhood between the rival branches of Islam was evident at the start of the prayer. Shias could be recognised among the Sunni worshippers, as they stood with their arms at their sides while the Sunnis held their hands crossed in front of them, each sect praying according to its tradition.
A woman stood to one side, tears streaming down her face. "Why are they killing us in Fallujah?" asked Wisal Fouad, sobbing. "The women, the children. Where is the freedom and democracy?" Asked whether she is Shia or Sunni, she answered in anger: "I am Muslim! We are the same."
After the prayer, Shia worshippers clamoured to identify themselves to this foreign journalist. "Najaf and Fallujah, we are together, we are brothers, and I came here to show that," said Wasim Ja'afar, 24, referring to the Shia and Sunni cities where clashes took place between Iraqis and western forces.
Displaying their identity at the Sunni mosque, many Shias held up prayer stones engraved with the name of Imam Hus- sein, the grandson of the Prophet Muhammad who is revered in Shia Islam.
"I usually pray near my house," said Muhammed Odeh, 18, from the Shia district of al-Showla, stone in hand. "I came here for the first time to show my support for Nasiriyah, Sadr City, Fallujah, Kut - all the governates of Iraq that are against America and Israel."
Some Sunnis also came out in support of the Shia uprising. "I am Sunni," said Umar Ali, 42, "but I consider Moqtada al-Sadr a great national leader." Across town, at the central blood bank, the blood that ran was only one colour, donors said.
"We are all one," insisted Hazim Ahmed, 44, as he emerged from the building with two cousins, their arms bent to stem the bleeding. "We must thank the Americans for this."
Ahmed refused to say whether he was Sunni or Shia. But he did divulge that he had donated two bottles of blood in his show of solidarity. "One for the Shias in Kufa that are being killed," he said, "and the other for the Sunnis in Fallujah."