Following a brief statement about the rescue on Sunday, the military said a total of 26 fighters were killed, seven wounded and one captured. The US side suffered seven wounded, it added.
The Iraqi fighters had set up an ambush on both sides of the road and were waiting for the convoy, which was heading to a military base south of Baghdad.
The convoy was under small-arms fire and rocket-propelled grenades about nine kilometres east of Salman Pak, when the US military police patrol arrived, said Major Rob Simmons on Monday.
"The patrol inflicted massive casualties on the attacking force. Total enemy killed in action is 26, and another seven enemy fighters wounded in action. Additionally, there was one enemy captured," Simmons said.
"The patrol suffered three wounded that were transported to the nearest medical facility, and another unit had four wounded in action."
Surge in violence
The attack came amid a surge in violence against the US-led military forces around Salman Pak, 25km south of Baghdad.
"In recent days, this route has had increased attacks on coalition forces," said Simmons, referring to the road to the capital which is littered with burnt-out cars.
There were also conflicting reports about the fate of an official convoy headed to the capital from Basra, Simmons said.
Separately, an interior ministry official insisted on Monday that 10 guards belonging to interim minister of state for governorate affairs Wail Abd al-Latif had gone missing on Sunday in Warda when Latif's convoy was ambushed south of Baghdad.
Latif's office has denied any such attack.
Meanwhile, Iraqi police detained a Syrian and a Palestinian on suspicion of planning an attack in Karbala, 100km south of Baghdad, said police sources on Monday.
Karbala is home to many revered
Shia religious sites
Police from the city of al-Musayab, 60km south of Baghdad, picked up the pair on Saturday when they attempted to enter Karbala, home to major Shia shrines.
Lieutenant Muhammad al-Masoudi said the men were members of al-Qaida and that they confessed to planning to launch a suicide attack in Karbala.