The helicopter attack on the village of Jurf al-Sakher, about 120 kilometres (75 miles) south of Baghdad, on Saturday provoked furious members of the group to quit en masse, according to their tribal leader Sabah al-Janabi.
"It was the third incident in a month. We have lost 19 men while 12 have been injured because of coalition attacks," Janabi said.
"The group, which comprises 110 members, resigned in protest at organised assassinations by the coalition forces," Janabi added.
A member of the group, Mohammed al-Rariri, 32, vented his anger at the incident.
"We have been badly affected and are very angry at this aggression," said Rariri. "Whether it was an error or intentional, it proves that the coalition is not worried about the stability of our area."
Another member, Abdallah al-Janabi, 29, accused the US military of deliberately sowing disorder so that they can stay in Iraq "for as long as possible."
"They ensure that chaos and terrorism continues by all possible means," he charged. "But we remain vigilant against those who want to kill our children and our families."
US military spokesman Rear Admiral Gregory Smith told a news conference in Baghdad that US forces had shot back after coming under fire.
"There was aggressive conduct by members of an armed group," he said.
Iraqi security force officials expressed alarm at the resignations of the Awakening members.
"(Their) withdrawal will create a security vacuum in the area," said Babylon province police chief Fadel Radad. "It will be necessary to boost military forces to ensure security is maintained," he said.
However, Abbas al-Juburi believed he could persuade Awakening members to resume their duties -- manning checkpoints, patrolling and being on the lookout for insurgents.
"We will try to use our excellent relations with them to convince them to resume their mission," Juburi said.
According to the spokesman for the Awakening at Jurf al-Sakher, Mishaan Hamid, meetings are expected soon with Iraqi and American military officers.
"It is certain that the withdrawal of our forces will result in a return of chaos and terrorism in the area," he said.
The Awakening groups began in western Anbar province when Sunni tribal leaders turned on their former Al-Qaeda allies in September 2006 and drove them out.
US commanders say there are now around 130 such groups across Iraq totalling about 80,000 volunteers, 80 percent of them Sunni Muslims and the remainder Shiite.
Güncelleme Tarihi: 18 Şubat 2008, 20:17