Iraqi officials are accusing the U.S. military of massacring at least 16 Shiite worshippers during a raid on a Shiite mosque Sunday night. The Guardian newspaper reports the killings have opened the biggest rift yet between the United States and Iraqi Shiites. Shiite leaders have suspended talks over forming a new Iraqi government. Iraq’s Interior Minister called the U.S. raid unjustified and horrible. The leading Shiite governing alliance is urging the U.S. to return full control of security to Iraqis. The Baghdad provincial governor has suspended all cooperation with U.S. forces. “The occupiers should be bought to account for this despicable crime,” said Sheikh Abdul Rahman Al-Shwaili. “It is committed by the occupiers against unarmed worshippers and we urge the Iraqi government to take an honest and positive stand towards this vicious attack against Islam and the worshippers Despite the political outcry, the U.S. military defended the raid on Monday. One official described it as a “hugely successful” operation against an insurgent hideout. The U.S. has denied its troops killed any Iraqis and said the massacre was staged.